Do you trust reach and stack ?

[Epicus07]

Hey guys,

Going to drive a long distance for a bike I really want but its a 52cm. I typically ride a 54-55 cm. I wouldnt think that this would fit except the reach and stack are near identical to my 54cm Roubaix. 374/582 vs 375/585. The seller is 2 inches shorter than me, using a zero setback post and a 90mm stem.

I'm hoping a regular post and a 100-110 stem will make this work.

Am i crazy ?

FWIW my bike fitter recommended that I look for a bike close to 375-385x and 585y

[semdoug]

"Trust but verify." Manufactures' numbers and peoples' measuring are always suspect but in your example it appears to be only 1-3mm difference.

[timto]

Stack and reach are more reliable than '52' vs '54'.

For instance one company might measure seat tube length center to center, the other center to top of top tube, another center to top of seat tube. There can be many cm variance between these three different '52's

Even in TT length - some companies show both Effective and actual TT lengths on sloping tt bikes. Some sellers mis-post one for the other.

Also size of tubing sometimes comes into consideration. A 52 CtC seat tube on a bike with skinny top tube is smaller than the same with a big fat top tube. FWIW I find Specialzed 54 to be 'short' compared to say a Pinarello 54 the latter being much taller of a bike.

[echelon_john]

Try to compare seat tube angles to make sure the reach # combined with the setback won’t require you to have your saddle in a funky position on the rails to get your setback correct, which would then throw off the saddle-to-bar reach.

[Clean39T]

Stack and reach, plus wheelbase and chain stays, and BB drop...and STA/HTA.

I've had too many bikes that should have been fine that weren't, and some that shouldn't have been, but were.

[nooneline]

Originally Posted by timto

Stack and reach are more reliable than '52' vs '54'.

Extremely this. I've ridden 52 cm bikes that are longer than some 54s. I've seen manufacturers that have a 48, 50, and 52 that have identical reach and nearly identical stack.

The question to ask is, I think, do you trust *only* the numbers as being a good indication of what you can expect from a bike?

[defspace]

Stack and reach are going to tell you the story as far as getting your hands, butt, and feet in the right positions. Sounds like you shouldn't have much trouble replicating your position.

That said, I'm starting to realize there's a lot more that goes on in geometry beyond making sure your hands, butt, and feet are in the right places.

I've had several bikes in the last few years that all "fit" the same - same contact points. Some of them I loved, some were just okay, one was terrible.

If you're talking about a road racing bike, it sounds to me like the previous owner may have been riding up a size. But even then, height doesn't tell you too much by itself. I think a lot of reach-space can be driven by spinal extension. Two people of the same body dimensions will fit a bike very differently if one rotates from the hips and one bends along the spine.

[velofinds]

How did it go?

[audiojan]

Stack and reach are based on reference points (everything is measured from the center BB to an agreed upon point on the head tube). the 52, 54, medium, etc. means absolutely nothing most of the time and is not comparable between brands (and sometimes not even models within the same brand!). Even if the number corresponds to a measurement you can find in a geometry chart that still isn't comparable to another brands measurement. There's simply no agreed reference point as to from and to where those measurements are taken.

Stack and reach will give you data that relates to real life and is comparable. If the bike you want is close to your ideal stack/reach, then get it.

Height is also a really poor measurement of bike fit... you can have two people of the same height fitting very differently. For example, a friend and myself both ride Pinarello F8. He's 2" taller than me and ride a 53cm with a 100mm stem. I'm on a 55cm with a 130mm stem. I just need lots of reach due to my physiology and he needs a lot of drop to fit his. And yes, both of us are professionally fitted.

[Epicus07]

Sadly, too small. rode great though.

even with my saddle pushed all the way back with a setback post and a 120 out front, I wanted just a little more room. I probably could have made it work but i'd rather wait for a bike that actually fits.

Thanks for the input guys. FWIW the stack and reach measurements were lifted from a younger version of my Roubaix so this may have changed over the years but I didn't think it would be that much.

[robertbb]

Well, no I don't :-)

I'm comparing two aluminum bikes - Ridley Helium SLA and Fuji Roubaix. The numbers are almost identical on all but stack... where there is a whopping 3cm difference. I can't figure out how... any gurus out there who can explain this to me?


Helium (S) Roubaix (M)
ETT 54.5 54.5
Stack 573 543
Reach 384 384

ST Length 510 500
HT Length 142 140

ST Angle 73.5 73.5
HT Angle 73 73

BB Drop 66 68

Wheelbase 977 978
Chainstay 405 405

[raisinberry777]

Originally Posted by robertbb

Well, no I don't :-)

I'm comparing two aluminum bikes - Ridley Helium SLA and Fuji Roubaix. The numbers are almost identical on all but stack... where there is a whopping 3cm difference. I can't figure out how... any gurus out there who can explain this to me?

Not a guru, but your numbers are wrong, the Ridley Helium SLA has a reach of 543mm and a stack of 384mm. You might have copied the 573mm from the next size up.

https://www.ridley-bikes.com/project/helium-sla/

[robertbb]

Thanks for that...

I was looking here:

https://ridleybikes-ridley2.netdna-s...sport_2017.pdf

You're right, it should be 543. Looks as though Ridley has themselves made the typo in the PDF...

I've emailed them to notify.

[robertbb]

Well... Ridley acknowledged the error in their PDF "passport" for the frame, and will be updating it. I jokingly asked for a discount for pointing it out and got knocked back

[mhespenheide]

Late to this discussion, but...

I trust stack and reach more than I trust "62x59.5" or the like, but as others have already mentioned, they're not the whole story. According to the pure numbers, my Felt should be a nearly-perfect fit. It's not. It's close enough that I've been able to make nearly-complete peace with it, but my position on it isn't quite what I would have expected from the numbers.

As a math teacher and numbers guy, it bugs me to think about. It bothers me that I can't figure out the discrepancy.