eduskator

I've always wondered why there are so many different recommendations for frame with similar geometries. How can this differ from a brand to another?

I'll lay out an example here:

Giant TCR (M/L) VS Specialized Tarmac SL7 (56cm)

Giant recommends 5'10'' to 6'2'' rider height for the M/L (equivalent of 56cm more or less) and 6' to 6'4'' for the L (equivalent of 58cm more or less)

Specialized recommends 5'9'' to 5'11'' rider height for the 56cm and 5'11'' to 6'2'' for the 58cm.



The TCR seems to be slightly higher than the Tarmac. Any ideas why Giant would recommend 3'' taller (5'11'' to 6'2'') for the M/L?

It may not be a big deal for some of you, but I've always been in between two sizes (56 and 58) and I do not like 58cm bikes because they feel too big and they come with wider handlebars and longer crankarms that don't suit my needs. This is why I usually go with 56cm bikes even if I am 6'1'' tall. I am fitted, but the only two downsides are the extra height of the seat post and more spacers between the head tube and the stem.

Sy Reene

Just speculating of course...

Like you've discovered for yourself, Giant acknowledges that some riders can and do opt to size down. Pros do this a lot and ride a bike a size smaller because they have the flexibility and core strength to deal with the more tucked and aero position. They also probably have no purchasing hurdles to overcome if they also want a custom length stem though.

Possibly on the flip side, Spesh now takes internet orders and ships directly to home -- maybe they've found it more successful to not raise any questions in potential buyers' minds about what size they should order (and therefore don't end up ordering at all), but rather have clear cutoffs where each size bike takes over exactly where the prior size left off?

PeteHski

There is no consensus between different manufacturers in how reach and stack should progress with frame size. I don’t have it to hand, but I read an article recently showing a graph of how different manufacturers change reach and stack across their size range. Some increase stack much more than reach and vice-versa.

Here you go, this explains it and uses both these bikes as examples.

https://www.myvelofit.com/fit-academy/brand-comparison-top-5-all-round-road-bikes

“The Giant TCR Advanced has six sizes ranging from XS to XL. Ths small number of sizes means the bike is limited in its overall breadth of fit and has relatively large jumps in sizing compared to the other models which have seven or eight sizes to fit you”

“Generally the Tarmac has consistent jumps between sizes other than a rather large jump between 54cm and 56cm.”

wheelreason

Horizontal top tubes in one centimeter increments...

Iride01 

There is no one perfect size bike for everyone that is the same height as you. Some people can ride a wide range of sizes with no issues or complaints. Some can't ride any size with out issues or complaints.

That's why one should ride bikes of different sizes before they buy. Or at least over years of owning several bikes in different sizes, they should begin to figure out what size is best for them.

tomato coupe

Why do shoes and clothing vary in fit from one brand to another?

Sy Reene

I think most are missing the OP's point/question. 2 bikes of essentially identical geometry are recommended by their manufacturers for different sized humans. Why?

tomato coupe

Giant typically recommends a 4 inch height range whereas Specialized recommends a 2 or 3 inch range. The recommendations aren't for different sized humans, just different ranges of human sizes.

bruce19

My take is that manufacturers realized that they could save money by going to the S-M-L system since it minimizes the number of frames they have to make. IMO this eliminates the variety of sizes needed for riders specific dimensions.

Sy Reene

Not really, at least sampling a few makers
Specialized offers 7 sizes: 44, 49, 52, 54, 56, 58 and 61
Giant offers 'only' 6 sizes: XS, S, M, ML, L, XL
Canyon seems to offer 8 sizes, from 3XS to 2XL

While Giant has one fewer number of sizes, I think this is just because they haven't opted to have an offering for the sub 5' rider. Otherwise >5' is pretty much represented by the same number of size offerings, which I imagine covers 98%+ of the market.

bruce19

I'm old enough to remember when frames were made in 2 cm increments. And, if you are going from 44 to 62 that would give you 10 sizes. Of course, I am also old enough to be mis-remembering it. According to Pinarello they offer 13 sizes. Colnago 14 sizes.

PeteHski

This is true. But when you compare the progression of stack and reach across those sizes (see the graph in the link I posted earlier) you will see that each individual manufacturer has quite differing ideas of how they should vary. As you noted they also cover a different overall range. Giant’s idea of XS is considerably larger than other brands and Canyon offer a couple of sizes that are larger than others XL.

Rider height is only a very rough indicator of frame size anyway. Most brands do have a slightly more detailed fit calculator available, usually taking account of inseam, height and sometimes even arm length.

eduskator

Thanks for your responses. Of course, it's always best to ride both sizes when you're undecided on a specific bike, but as you may all already know, it's almost impossible to test-ride a bike, especially at a 5k+ price range.

I prefer a large (58cm) frameset on TCRs and ML (56cm) frameset on Propels. Stacks and reach are identical from a bike to another (respective to their frame sizes) so it tells me that my body is OK with a specific range of stack and reach.

58cm bikes come with longer / wider components and that's what I don't like about them. For an ideal fit and feel on a TCR and most likely on a Tarmac as well, I would need to buy a 58cm + pay an extra to get the 42cm bars & 172.5mm crank arms. It would be nice for more manufacturers to offer the customization at this price range, like Orbea does.

PeteHski

Some do, but even that is not consistent across brands. My Large (58) Canyon Endurace came with a 420 bar and 172.5 cranks. While my Large Defy had 440 bars and 175 cranks. FWIW I can’t tell the difference!

I do like Orbea’s semi-custom approach, but when I attempted to buy one there was zero stock in my size preferences. Although this was early 2022 with pandemic shortages.

eduskator

44cm bars is wide AF for me. I was hoping that manufacturers would adjust to the new trend (narrower bars) and would equip their 58cm bikes with 42cm & 172.5mm crank, but whatever!

crazyravr

What you describe is the exact reason why me at 6'2" went from a Large to a M/L TCR. All I had to do was to throw on a 120mm stem. Perfect. On the Large I felt way to stretched out, the cranks were too long, well pretty much everything was just too wide and long.

eduskator

Yeah, there's just the seat post sticking out of 16'' that bothers me. Odd looking bike if you ask me. The top tube angle is intense! I wish I had shorter legs lol.

I liked my 58cm TCR better, but I would have needed the components of the 56cm in order to have a ''perfect'' feel and fit.

wheelreason

They don't, they just apear to because the numbers (or letters) don't mean the same thing.

shapiroeric

Invest in a fitting.....I am 5'9" and ride a 48....

eduskator

All expensive bikes I've purchased had an included fitting from a physiotherapist, and that's not the point of this thread.

48cm at 5'9'', you must have abnormal leg and/or arm length and/or a s*it load of spacers between your frame and you stem.

PeteHski

Some manufacturers are more conservative than others. Canyon Ultimate has 410 bars and 172.5 cranks in Large. My Endurace L has 420 bars and 172.5 cranks.