Choosing the correct size road bike – Geometry Explained

Shopping for a new bike is an exciting time. But, when faced with a vast choice of bikes, all available in a variety of sizes. How do you pick the right size for you? Choosing the correct side road bike couldn’t be easier. As long as you are armed with the right information that is. Read our guide to find out what works for you.

Women-specific bikes

We like to think of all riders as being individuals, and our priority is in making sure that the bike is right for your body shape, size, and personal preference. Consequently, all of our bikes are of a unisex design and are fully customisable to achieve a fit that’s perfect for you. The crucial element to getting this right is to ensure that the sizing of key components is correct. These being the handlebars, handlebar stem and cranks. Specifying a ladies specific saddle is always highly recommended too, of course.

Back to basics

Firstly we should address what exactly is meant when we refer to ‘geometry’. In short, it is simply this; geometry encompasses the shape, length, and angles of the tubes that come together to form the frameset.

For example, the image to the right shows each tube represented by a letter. In the table below, each letter is linked to a specific dimension for each frame size.

The geometry of a bike affects the position you will find yourself sitting in, how the bike handles and its aerodynamic performance. A racing cyclist, for instance, seeks a more stretched out position for better aerodynamics. A mountain biker, on the other hand, needs a more comfortable, upright riding position. One that offers a head-up riding position to enable them to pick their lines as well as enhance stability and control.

1. Measuring your height and inside leg

The first step is to determine your height and inside leg measurement. Do you know these? If not, we have you covered. Here are some simple tips to help you determine these. The methods described below are easier with a helpful assistant. However, you can also obtain the measurements yourself in the absence of a willing volunteer.

Height

  • Simply stand upright in bare feet, with your back against a wall/doorframe.
  • Place a pen or pencil atop your head and parallel to the floor.
  • Make a small mark on the surface and measure.

Inside Leg

  • In bare feet; stand upright with your back against a wall.
  • Place a book/ruler between your legs and level with your crotch.
  • Have someone measure the distance from the top of the book/ruler to the floor.

2. Frame Size

OK, now that you have your height and inside leg measurements, it’s time to apply them to your bike of choice. The good news is that we have done the hard part for you. Each bike on our website has a recommended height range for each individual frame size (see image). This height range isn’t just based upon default factory measurements. We have collated data gained through numerous real-world measurements taken in-store and through test rides.

If you find that you fall between 2 sizes, the general rule is to opt for the smaller size. Why you may ask? Well, it’s because it’s generally considered easier to make a smaller bike fit. There are certain alterations that you can make to a smaller bike to correct the sizing. These include lengthening the stem length, crank length and raising the saddle height. It is much more difficult to adjust a bike that is too large to fit the rider. After all, a seat post can only drop down so far and fitting too short a stem can result in overly responsive steering.

Alternatively, if at all possible, we would thoroughly recommend popping into one of our showrooms to speak to one of our friendly and knowledgeable experts. Each showroom is fully equipped with a measuring jig. Upon which we simulate the dimensions of a frame and adjust the fit to get it just right for you.

However, if visiting a showroom is not possible, we can also deliver the showroom experience direct to you. Simply connect to one of our Live Instore Experts via a live one-way video call. Our experts can answer any queries you may have, offer advice on sizing and component choice or even showcase the bikes. All from the comfort of your own home, and remember it’s completely anonymous. You can see us, but we cannot see you.

To connect with a Live Expert simply visit our website and click on the image in the bottom right corner of the screen.

3. Key Components

As we alluded to earlier, there are several key components that are customisable and which ensure that the bike you receive is right for you. Whether you’re male or female, the rules to obtaining the correct measurements apply to both equally. Unlike an ‘off-the-peg where the components choices are preset, we offer a wide choice of customisation options.

Handlebar width

Have someone measure the distance between the ac joints of your shoulders (the 2 knobbly bits to the front of your shoulder, where the collarbone and shoulder blade meet).

With the odd exception, most handlebar manufacturers will quote handlebars widths as a centre to centre measurement. This dimension is normally obtained by measuring the bars from the centres of each drop.

If they are a centre to centre model, (like our own LEVEL brand) simply add 2cms to your shoulder measurement to obtain the correct width. If they are measured from outside to outside of the drops, add 4cms.

The 2 most common ways that manufacturers denote bar width is centre to centre or outside to outside

Handlebar stem

Unlike handlebars, there is no magic formula to help you ascertain the correct length of the handlebar stem. The only way to accurately determine this is to get a professional bike fit or visit one of our showrooms. Given the general trend of female riders being shorter of torso and longer of leg, we find that a shorter stem length works better. The average male rider will normally opt for a stem length of between 90 and 120mm. We find a stem length in the region of 70-90mm is better suited to the female rider.

Generally the smaller the size of the frame, the shorter the stem should become. When you select a frame size on our website it will automatically default to our recommended handlebar width and stem length for that particular size. However, should you then change the size, these will decrease or increase correspondingly. You then have the option to amend these manually by clicking on ‘customise bike’.

Crank Length

The length of the crank arms (the bit that your pedals screw into) can have a significant impact on both comfort and performance. Choosing the correct length of cranks can help prevent sports-related injuries, increase power transfer or make climbing easier. Too long and you could find your knees clattering into your chest on the upstroke. Too short and you could find yourself losing out on the valuable power output generated by your long levers.

The most common choices offered are; 165, 170mm, 172.5 and 175mm (this measurement is taken from the centre of the pedal axle to the centre of the cranks, as per the image above). The commonly held belief that the size of the bike should dictate how long the cranks are is a bit of a myth. Riders who require smaller bikes in the XS/Small range will definitely benefit from shorter cranks. But in practice, it all comes down to personal preference as much as it does the size of the bike. There are, however, a couple of formulas for determining what length of cranks would work best for you.

Firstly, this formula calculates crank length based on 9.5% of your total height in cms. If we take a rider of 185cms height, for instance, 185×9.5= 17.575. So, a 175 crank would be the ideal option for that rider. To muddy the waters slightly, this does not mean that this rider must only ever use 175 cranks. They may prefer a faster-pedalling rhythm (cadence) and in this instance, a slightly shorter crank would be more to their liking. A faster cadence is less impactful on the muscles but it could be less efficient at cranking out the power.

Secondly, there is the inseam method. Take your inseam measurement in cms and multiply by 1.25 then add 65. If your inseam is 83cms then it works out as 83 x 1.25=103.75+65 =168.75. So, using this method you would round up to the nearest crank length of 170mm.

Saddle

As individuals, our anatomies are all very different. What may be comfortable for one person may cause discomfort for another. This makes it very difficult to pinpoint exactly what saddle will be comfortable for you. What is essential though is to ensure that it offers the right support for your sit bones (pelvic bones). Thankfully, there is a very simple method for measuring how far apart your pelvic bones are. All you need is,

  • A flat bench or chair to sit on
  • A flat object that sits lower than the seat, that you can rest your feet on. A stool, box, or bench for instance.
  • Piece of corrugated cardboard.
  • Tape measure.
  • Chalk (optional)
  1. Take the cardboard and lay it on the seat.

2. Lower yourself onto the cardboard so it is aligned under your buttocks.

3. Raise your feet and place them on the lower footrest.

4. Try to simulate the position you would normally adopt when riding a bike. If you like a relaxed position sit more upright. If you prefer a more aggressive race position lean forward.

5. Hold this position for approximately 30 seconds.

6. Stand up and retrieve the piece of cardboard.

7. You should be able to make out 2 clear indentations imprinted upon the cardboard. These are produced by the sit bones and can be used to calculate your ideal saddle width. If you can’t make out the indentations clearly take a piece of chalk and rub it across the cardboard to bring out the indentations.

8. Next, take the tape measure and measure the distance between the indents. Using the centre of each as your start/finish points.

You can now apply this information to choose an appropriate saddle for your preferred style of riding. All saddles have a defined width so just find the one that best suits you.

Hybrid/Gravel/MTB

Add 20mm to the measurement, this will add more stability and comfort when assuming a more upright riding posture

Endurance Road/Gravel

Add 10mm to the measurement, this saddle offers a good compromise between comfort and performance.

Further assistance

We hope that this guide has been of assistance to you, and helps you to work out what sizes you need.

Instore

However, there’s no better way to perfect the sizing and fit than to come in and see us. That’s why we now have multiple showrooms located across England. Visit us for personal sizing guidance and to receive excellent buying advice from our team of friendly, professional and knowledgeable experts. Not to mention that you also get to see our range fo bieks inthe flesh of course.

Situated in the heart of the Ribble Valley, our Clitheroe showroom offers you a bike shop experience like no other.

We can also be contacted through the usual channels;

By Video Call

By far one of the best ways to get in touch is to use the Ribble Live In-Store Expert function. This service brings the instore experience direct to the comfort of your own home. Simply click on the icon that appears at the bottom right corner of the website to be connected to one of our Instore Experts who will be delighted to assist you via a one-way video call. You see us but we cannot see you. They can take you through everything from sizing to build options and even offer close-ups of the bikes and equipment on their hand-held cameras.

Customer Service

Our customer service team is available to take your call 7 days a week and until late in the evenings on weekdays. Contact the team directly for friendly advice and assistance.

Social channels

You can also contact us through the usual social channels, by direct message through Twitter, or private message us through Facebook, Whatapp or Instagram.


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34 Comments
  1. Hi, I’m interested in buying the Ribble Sportive Racing from the Ribble site. However, I’m quite confused about sizing.

    The chart size recommendation on this post conflicts with the information given on your frame size help page http://www.ribblecycles.co.uk/text/framesize.html

    I’m 5’11 and have a 33″ inseam ( 83.82cm ). According to the SLOPING GEOMETRY formula on this page ( 83.82 x 0 .64 = 53.6448cm ), I should be getting a 53cm sized frame. While the chart on this page suggests I go with a 56cm.

    The 53cm sized frame’s top tube is 558mm, matches more closely my current 56cm sized frame with a 560mm top tube. But now I’m not sure which to get.

    So which is right? and which do you reccommend?

    Thanks!

    ——————————————————————–

    “SLOPING GEOMETRY (Sloping Top Tube)
    Use the formula: Inside leg measurement (cm) x 0.64. The resultant size and round up or down to the nearest frame size option. If you are in between sizes we recommend you go for the smaller size.”

  2. Hi
    I am looking to buy my wife your clearance 2016 Evo pro carbon ultegra. What is the top tube length of the XS and S sizes? She is 5’4″ tall and presently rides a frame with top tube 54cm with 8cm stem and she is too stretched out.

  3. I’m 5’7” I’m looking to buy a a ribble TT bike what size frame should I go for?

  4. Hi, I am a sportive rider. I am 6ft with a 33 inch inside leg. I have a medium genesis zero 2015 frame currently. I felt the large was too big with a long top tube. The medium tt is 565mm with the large being 585.
    Felt like I was reaching on the large frame.

    So am looking at buying an upgrade. Will buy the sloping frame and that would put me at just over 53 cm based on your sportive chart. I note the toptube length would also seem consistent with my current bike.

    Can you confirm this is right? Whenever you look at height measurements on other sites it suggests 58 + so just eanted to be clear before I buy, thanks shaun

  5. My size is 171 height and 80 cm inseam leg, The ST of my Ribble Sportive Racing Green Carbon 2017 is 48 cm and the horizontal top tub 52 cm.

    Is that Bike too small for Me?

    Please Advise

  6. I currently have a volt pulse. It basically has 4 power settings, put simply:-
    Setting 1 gives assistance up to 5 mph
    Setting 2 up to 8 mph
    Setting 3 up to 12 mph
    Setting 4 up 15.5 mph
    This system wastes battery power as I don’t really need assistance to get up to 8 mph. For example, I would prefer the motor to kick-in after I get to 8 mph.
    Can you tell me how your e-bikes deliver their power?

  7. Hello I have a gran fondo size M.
    Please can you tell me how many cm this is as I’m looking to sell it
    Thanks!

  8. Hi, I have just very kindly been given a Ribble, it looks awesome but is going to take a lot of TLC to get back on the road. I pretty certain its a road bike but please how do I identify what type it is?
    Cheers
    Paul

  9. I am looking to buy an ebike for my wife, but she is only 5’1″. Would an XS for the CGR work? What us the stand-over height on that?

  10. I want to buy the CGR AL, I have a question on advertised bike weights which is a bit confusing. The CGR 725 medium with Tiagra is advertised weighing 10.65 pounds, whereas the CGR AL Tiagra medium, and a lighter frame is shown to be 11.5 pounds? Is this correct and if so what is it that constitutes the extra weight please?

  11. Good Morning,

    I am considering ordering a CGR 725 and I’d like to confirm which size bike might be best for me. I measure 68.5” tall with a 30“ in seam. What size bike would you recommend? What length of handle bar stem and length of crank arm might be most appropriate? Thank you.

  12. I am looking for an Endurance set up – however, the Stack / Reach for the Endurance frames for a Medium build are S 541 and R 390. That does feel like an Endurance set up – I currently have a BMC with a 559 / 383 and that feels a bit of reach.

    Am I mis-reading something in your geometry charts ?

  13. Hello – I’m looking at buying a new bike. My height is 170 cm so I’m between small and medium. I currently have a hybrid bike (Canndondale quick 2) where I had the same dilemma and ended up buying the small frame but I’m finding it uncomfortable on longer rides.

    Which size would you recommend?

    Height: 170 cm
    Inside Leg: 75.5 cm

    Thank you

  14. Hi Ibrahim,
    Thanks for getting in touch, not all bikes will have the same recommendation based on your height as the geometry of the bike will affect what size you would require. We would need to know the style/model of bike that you were considering to provide such a recommendation. If possible, why not speak to one of our bike experts who can guide you through the sizing for any bike from across our range.
    Best Regards
    Team Ribble

  15. Hi,

    I am riding a gran fondo 2 ( circa 2010) loaned by a friend. I am 177cms high and 84cm inside leg,

    your formula says a 54, the fondo I have has 535mm top( c) and seat post to crank (a) is 520mm. Can I assume this is then a medium?

    It does feel a tad small, as I feel very cramped . I put the seat quite high to get legs right but still feel a bit cramped, when I hold the drops i get back ache so have to ride more prone to stop this.
    I cant get saddle back any further. Stem is 100mm

    I am 62 so although fit perhaps back is not as supple as a 35 yr old who lent me the bike!

    It is very fast compared to Allez but feel if i stick with it i will get backache long term. I currently ride Specialised Allez 56cm heavier but don’t get back ache.

    Would you suggest a slightly larger frame would be ok, and is the geometry of current frames similar, and could you suggest a frame? Happy to build as a project or off the peg.

    tkx

    Paul

  16. Hi Paul, thanks for getting in touch.
    From launch to 2017, the Gran Fondo’s geometry remained unchanged. It was available in 5 sizes; 44,49,52,55 and 58cms which was measure from the centre of the cranks to the top of the seat tube. The respective height recommendation for each frame was 44cms=5ft to 5’4″, 49cms= 5’4″ to 5’6″, 52cms= 5’6″ to 5’9″, 55cms= 5’10” to 6’1″ and 58cms= 6’2″ to 6’4″. I’m not sure when you state that the seat post to crank measurement is 52cms, do you mean where the seat post enters the frame? If so that would make it a medium which would have been our height recommendation at the time and which proved to be very accurate. Having compared the relaxed geometry of the Allez to the old 55cms Fondo it is a closer match in terms of the top tube and head tube lengths. The most similar in terms of geometry to the Allez 56cms is the CGR range of frames in a size Medium. The CGR works out as being 7mm shorter in the stack and 5mm shorter in the reach.
    If you need any assistance with sizing it is very much worth contacting our helpful team of In-Store Experts.
    Best Regards
    Team Ribble

  17. Bonjour, j’ai une dimension axe pedalier / dessus de selle de 765mm , quelle taille de cadre de velo me conseillez vous pour un ENDURANCE SLR DISc?
    Actuellement j’ai un Pinarello F8 Dogma de taille 515 mm.

    Merci

    Olivier
    -FRANCE-

  18. Bonjour Olivier,
    Merci de m’avoir contacté. Le petit cadre de taille correspond presque parfaitement au Pinarello F8. Le cadre Ribble est 5 mm plus long en portée, tube de direction, tube de selle et 5 mm plus court dans la pile. Cordialement, L’équipe Ribble

  19. Hi Amanda,
    Thanks for getting in touch, the height range for a particular collection of bikes will differ depending upon the style of bike and difference in geometry. For instance, it is not possible to produce an electric bike equipped with the ebikemotion system that suits anyone below the height of 5’2″. The internally mounted battery physically prevents us from shortening the tubing enough to accommodate the battery. For this reason, we now produce a range of e-bikes with a dropped top tube that will accommodate a height range of 5ft and upwards. If you advise us what sort of bike you are looking for, we can advise you of what is most suitable for your needs. If you feel happier speaking to us what not contact one of our friendly and knowledgeable team using our live chat service or Live In-Store Expert services?
    Best Regards
    Team Ribble

  20. Hi Claire,
    Thanks for getting in touch,
    Our offerings are sadly limited but in terms of out and out road-specific frames, there is the R872, available with rim or disc brakes. If you want something that is highly capable on-road and off it, then there is also the CGR AL. If you need further guidance or sizing advice why not talk to our Go In-Store team who can give you excellent sizing assistance via a one-way video link. They also happen to be available 7-days a week and until quite late.
    Best regards
    Team Ribble

  21. Hi. I am considering my choice between cgr ti/725 or endurance ti. Endurance does seem to be almost the same thing except tyre clearances right? Meaning if i get 32mm tyres it could manage some lighter fields and smoother gravel on the climbs right?

    I am 167cm tall with standover of 76 cm. Am looking at ghe XS size according to your charts. What size of groupset option regarding diameter would you advise please?

  22. Hi Martin,
    Thanks for getting in touch,
    The Endurance and CGR Ti may look visually quite similar but they are very much two different frames that are designed to do two very different tasks. The Endurance Ti is a road-focused platform that offers the rider a more aggressive position that enhances its on-road performance which includes clearance for tarmac specific tyres. The CGR on the other hand is significantly taller at the front end to provide more confidence and control when a ride heads off the beaten track. It also offers far more tyre clearance to offer the flexibility to fit off-road tyres as well as road tyres. Can you use the Endurance Ti off-road? Well yes, you could, however, the tyre choices will be very limited so it would need to be ‘lighter’ routes. At 167cms tall that would indeed put you on the XS CGR or Small Endurance. Sorry, I’m not too sure what you are asking in terms of the groupset, can you clarify, please?
    Best Regards
    Team Ribble

  23. Dear Ribble Team,
    I am interested in your Endurance SL R Disc, and have a question regarding the bike frame size. I am 194 cm tall (with an inside leg of 93.5 cm). You recommend your XL frame up to a height of 191 cm. Can you still recommend the XL frame to me, eg with a longer stem? Do you have experiences with riders > 191 cm using your/this bike)?
    Best Regards

  24. Hi Alex, thanks for getting in touch,
    We do have a member of the Ribble team who is 196cms and he rides the Endurance SL R. He loves it because he is more of a fan of the slightly more aggressive endurance racing style of geometry. He does have the longest option of the LEVEL 5 bars fitted (135mm) so it all depends on how relaxed you wish the position to be.
    Best Regards
    Team Ribble

  25. Hi,
    Thanks for getting in touch, The Adventure 725 was discontinued in 2020 and we now only have stock limited stock of size medium in this spec left; https://www.ribblecycles.co.uk/ribble-adventure-725-sram-gx-eagle/. The Adventure range was replaced by our gravel range for 2021, though we do not offer a steel option. You can view the grave range here, which all include the carryall fork mounts. https://www.ribblecycles.co.uk/gravel-range/
    Best Regards
    [email protected]

  26. Dear Ribble Team

    I have just ordered a bike with you but i just need clarification if i have asked for the correct size stem for my bike. I am 5 feet 10 (just) and have ordered a 100mm stem. Do you think this will be adequate for me? or should i go for a 110mm stem? If you think i need a slightly larger stem how do i go about amending my order please? Any help appreciated

    Leon Blunden

  27. Hi Leon,
    Thanks for getting in touch, short of having a bike fit, determining which stem size you will require is an educated guess. To offer you a better idea of what size would best suit you, I would need to know –
    a) which bike you have ordered
    b) which size you have opted for (if in between sizes)
    c) your inside leg, if you are proportionally longer in the leg than torso this will affect stem length.
    If you can please provide this information I can advise you accordingly.
    Best Regards
    Team Ribble

  28. Hi,
    Thanks for getting in touch, a great question and sadly one that I have no answer for at this moment in time. I have been provided with a tech drawing of the bars which offers plenty of information except the obvious dimensions of reach, drop, and angle! I have contacted the designer for these dimensions and will contact you once I have this information.
    Best Regards
    [email protected]

  29. Hi Ribble Team,
    I’m interested in Ribble Ultra SL. I’m 178.5cm tall with 84cm inner leg. According the geometry table M size with 90mm stem should fits me.
    What is min/max seat hight please?
    What is stem angle and handlebar reach?
    Which derailleur hanger should I order as a spare part?
    Is or will be the bike UCI approved?

    Thank you for the reply, just waiting to finish the order =)

  30. Hi,
    Thanks for getting in touch, sadly I’m not able to supply minimum and maximum saddle heights as this is not a dimension that features in any geometry. I’ve asked my Go-Instore colleagues to get these dimensions and we’ll email them over ASAP with the rest of the details that you have requested.
    Best Regards
    [email protected]

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