Would a 17.5" 29er be too big?
 

I've been wanting to get a Trek/GF Mamba for a while now and I found one locally for $700 OBO. When I test road a Marlin, before deciding it would be better to go with a Mamba, I rode a 15.5" and when I stand over it I'm basically touching the top tube. I know 29ers are taller out of necessity but I didn't know if the bike would just be too big then. My road bike is a Trek 1000 and it's a 52 cm. I know when I checked geometry between by 52cm and a 15.5" they were about comparable. So would it be a bad idea to get a bike that's one size bigger?

Thanks in advance!

Yes, a 17.5 would be too big. Standover clearance really doesn't matter that much but the bigger frame will also be longer and you will be too stretched out. 29ers are not necessarily taller in the same size frame: the bottom bracket is lower relative to the axle to maintain the same distance from the bottom bracket to the ground.

Thanks Thor. I know there are some ways to shorten that top tube distance by adjusting the saddle forward & reversing the seat post so the clamp is in front, and maybe shortening the headset. I think 600-700 would be pretty good for a year old mamba, but I know I need it to fit in order to get good performance from it and enjoy riding it.

You can mess with the stem and get higher bars, but changing the fore/aft position of the saddle won't do it. Reason being is that when you stand, really only where the bottom bracket is matters, and you aren't changing that. Plus if you put the saddle too far forward, when you do sit, it'll be in a weird position for pedaling.

And I disagree that standover clearance doesn't matter. I've heard that before, but I've also found myself doing a quick dismount and ended up straddling the top tube before.

Thanks everyone. Tomorrow there's a local canoe, kayak, bike swap and I'm hoping I might find something good. :-)

I agree with your disagreement. :lol:

Seriously. I do agree w/you. I think we hear the "doesn't matter" line as backlash against the overuse of standover as the one-and-only measurement. I like to look at top-tube as first number, and then secondarily at standover.

To the OP: 17.5" is probably the most common frame size out there. It should be easy enough to find that size frame to try out.

You might even prefer a 26er, but that is a heretical statement that I will disavow having made. ;)

Standover does matter for short folks on 29ers, because you actually have to be able to straddle the thing! I just went through the 29er selection process and found for the first time that standover was something I need to pay attention to. All companies measure a little differently, so it's good to be able to look at all the numbers, the most important being top tube length and standover. On a 29er, stack height matters, also, since in the smaller sizes the bars can get pretty high.

I usually ride a 52 on the road and just got a 16" Salsa El Mariachi Ti. Fits me like a glove, but I have long arms and torso, so it could be different for you.

Good luck canoeing on the local mountain bike trails. Sheesh! Has the the FAQ learned you nothing?

Thought about getting a Mamba last year. I'm 5'7" on a really good day, but with short legs and long arms/torso. The 15.5 was decent in standover but really cramped for me in reach. The 17.5 felt good when I was rolling on it but I couldn't even straddle the bloody thing. Okay, that did not sound good:innocent:
I'd be wary about messing with the saddle fore/aft like Zephyr was saying. You could mess yourself up biomechanically doing that.
Standover height definitely does matter for sure. I'm still riding my old 26er for a reason.