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Bike Sizing


MarkDG
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Hi All

 

I am looking for someone who can measure me and advise what road bike and triathlon bike size I should buy. Taking into account more than just my height and in seam as from various articles I have read, stack and reach are important factors to consider.

 

All the services I have found require you to bring in your bike. I dont want this, I want to be advised what size to buy, assuming I would be advised on stack and reach and maybe other important geometries.

 

I have been reading many topics regarding sizing and the more I read, the more confusing it is becoming and I am now of the opinion that I would like professional advice as different manufacturers have different measurements and therefore, a 54cm from one manufacturer can be a 56cm from another.

 

As we all know, bikes are not cheap and I would therefore prefer to make the correct purchase.

 

I did go to a reputable bike fitment place in JHB for a so called sizing advise prior to purchase, but I feel the service was poor and it was a rushed job, no more than 20-30 minutes and walked away with my in seam, bar width and been told I am a 56cm, which many calculators online could tell me.

 

If anyone can advise where I can go or can provide me with sizing and fitment information, it would be appreciated as maybe I completely misunderstand the concept of proper bike sizing.

 

Like this calculator, but it said I am a 56-57cm road bike and a 46-48cm TT bike using the same measurements. I have emailed them asking if I have done something wrong.

 

https://www.competitivecyclist.com/Store/catalog/fitCalculatorBike.jsp

 

 

 

https://www.bicycling.co.za/health/10-bike-fit-myths-busted/

 

https://www.slowtwitch.com/Bike_Fit/Road_Bike_Fit/Reasonable_bike_fit_expectations_3595.html

Edited by MarkDG
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Hi Vetseun, thank you. I appreciate the reply. My concern with that is, a bike shop will obviously only sell me a bike brand they sell. Whereas, a different brand might fit better. Maybe I am incorrect.

Honestly, I'll probably be buying second hand.

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Unfortunately there's a personal factor too that the bike shop has to rely on you for - you can likely ride a 54 or a 56 equally comfortably with only slight changes in the setup. The reach (key measure) will only differ by about 1.5cm between these 2, and that is easily taken up by your choice of seatpost and stem. 

 

Other hubbers may differ, but you should look at a smaller frame if you're fitter/more agile and you can hold a more aggressive position. The bike will also be more responsive. A larger frame will be more stable (e.g. under power), and more forgiving on your lower back if you're less flexy. Also larger is going to go easier on you on longer rides.

 

I ride anything between a 53 Pinarello and a 56 Specialised. Both are just about perfect. The common measure to each is a frame reach of about 380mm.

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Hi Vetseun, thank you. I appreciate the reply. My concern with that is, a bike shop will obviously only sell me a bike brand they sell. Whereas, a different brand might fit better. Maybe I am incorrect.

Honestly, I'll probably be buying second hand.

All bike brands will have a frame that fits you. Don't worry about that aspect of it.

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Unfortunately there's a personal factor too that the bike shop has to rely on you for - you can likely ride a 54 or a 56 equally comfortably with only slight changes in the setup. The reach (key measure) will only differ by about 1.5cm between these 2, and that is easily taken up by your choice of seatpost and stem. 

 

Other hubbers may differ, but you should look at a smaller frame if you're fitter/more agile and you can hold a more aggressive position. The bike will also be more responsive. A larger frame will be more stable (e.g. under power), and more forgiving on your lower back if you're less flexy. Also larger is going to go easier on you on longer rides.

 

I ride anything between a 53 Pinarello and a 56 Specialised. Both are just about perfect. The common measure to each is a frame reach of about 380mm.

 

100% on reach... also consider stack - will determine how 'bendy' you need to be. Those with dodgy hips and necks fair better with less reach and more stack.

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Hi All

 

I am looking for someone who can measure me and advise what road bike and triathlon bike size I should buy. Taking into account more than just my height and in seam as from various articles I have read, stack and reach are important factors to consider.

 

All the services I have found require you to bring in your bike. I dont want this, I want to be advised what size to buy, assuming I would be advised on stack and reach and maybe other important geometries.

 

I have been reading many topics regarding sizing and the more I read, the more confusing it is becoming and I am now of the opinion that I would like professional advice as different manufacturers have different measurements and therefore, a 54cm from one manufacturer can be a 56cm from another.

 

As we all know, bikes are not cheap and I would therefore prefer to make the correct purchase.

 

I did go to a reputable bike fitment place in JHB for a so called sizing advise prior to purchase, but I feel the service was poor and it was a rushed job, no more than 20-30 minutes and walked away with my in seam, bar width and been told I am a 56cm, which many calculators online could tell me.

 

If anyone can advise where I can go or can provide me with sizing and fitment information, it would be appreciated as maybe I completely misunderstand the concept of proper bike sizing.

 

Like this calculator, but it said I am a 56-57cm road bike and a 46-48cm TT bike using the same measurements. I have emailed them asking if I have done something wrong.

 

https://www.competitivecyclist.com/Store/catalog/fitCalculatorBike.jsp

 

 

 

https://www.bicycling.co.za/health/10-bike-fit-myths-busted/

 

https://www.slowtwitch.com/Bike_Fit/Road_Bike_Fit/Reasonable_bike_fit_expectations_3595.html

 

 

 

You want professional advice but don;t want to see a practioner or professional....no wonder it's confusing....

 

Sizing between road and tri bikes is not the same. There is a much wider window of set up that works on the tri bike. The tri bike is also sized differently as the stack will be much lower to accomodate the raised arm rests. 

 

What you need is a practioner that can conduct a dynamic bike fit i.e. one where you are pedalling your current bike on a smart trainer at constant load and is able to measure the impact of the angle of your torso to hips to femurs to determine where your producing the best power range and then able to transpose that onto a tri bike. 

the only place I know that can do this is the Sports Science Institute in Newlands, Cape Town.

 

otherwise you have to figure it for yourself through test rides. Its not an easy process if you want to be very precise about it. If you are able to rent a tri bike of similar size to your road bike then you can start playing around by going for a few long rides on it to see what you body is telling you how it wants to be positioned.

You will find that if the bike is too long your back and upper arms will start too feel discomfort and you'll be pulling yourself forward. Great  that means the reach needs to be shorter.

Seat tube angle will influence the saddle height a lot on a tri bike so start with the same saddle heights as on your road bike an work from there. Once you have the reach sorted you can start to play around with how low  your can position the bars before you start to lose power and  go slower.

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Good Day DieselInDust, firstly, thank you so much for the information. I will get in contact with The Sports Science Institute. I think there is a misunderstanding. I definitely want to seek professional advice, hence my post. What I was asking was if anyone knew of a place or professional service offered whereby I am advised what bike size to purchase without having the bike yet. A service that is offered taking into account reach, stack, etc and not only height and inseam.......because from what I have read, there is more to sizing than just height and inseam. Maybe I am over thinking the topic, but, spending R20K plus is a lot of money and I do suffer a bad back and knees and dont want to make the incorrect purchase.

 

Thank you everyone for your input

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Good Day DieselInDust, firstly, thank you so much for the information. I will get in contact with The Sports Science Institute. I think there is a misunderstanding. I definitely want to seek professional advice, hence my post. What I was asking was if anyone knew of a place or professional service offered whereby I am advised what bike size to purchase without having the bike yet. A service that is offered taking into account reach, stack, etc and not only height and inseam.......because from what I have read, there is more to sizing than just height and inseam. Maybe I am over thinking the topic, but, spending R20K plus is a lot of money and I do suffer a bad back and knees and dont want to make the incorrect purchase.

 

Thank you everyone for your input

 

 

Sports Science Institute is the place to start. If you can, try to get to speak to Dr. Jeroen Swart. He has also developed a bike fit system and will know which JHB vendors have been trained and have the equipment. Any trained vendor should be able to put you onto a demo bike and determine the appropriate measurements that will guide your purchase decision

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