So I'm looking at a second hand frame. It's too big for me by normal standards, ie 20" v my usual 18".
As current thinking is that a short stem/long TT for full sus is a good thing, will I be OK with just running my seatpost a bit low. No Dropper BTW.
Will I die.
Yes
No
Maybe?
Need more information but surely you can answer the standover question incredibly easily?
seat tube size ie 18" or 20" means nothing.
Go on TT length and stand-over.
If it is a bit too big then forget it. It will never be right and you will be wasting your time and not getting full enjoyment which is the most important thing.
Riding a bike too big is worse than too small, ask my son.
Too big - not good
If you're not using a dropper the only thing that should really matter to you is the reach and whether you can get a short enough stem to make it fit. Gaps between frames are typically 20mm so a 50mm stem becomes 30mm for the larger size frame. For me this is a much more acceptable adaption than a frame that's too small and needs a longer stem.
"To big" is very subjective, I don't think you can define it by one measurement. I've ridden bikes from 17.5" to 20" without any problems. Reach, head tube and standover are more important.
Too big = bad. Big =/ too big. As long as it's not stupidly long, got decent clearance, and you can drop the saddle sensibly it's probably going to work fine (I've been considering upsizing my current frame by a size, just to get the longer TT, but then I know it'll still have a low TT and lots of seatpost drop.)
Hmmm, looked into geometry for the frame, and I reckon it'll be too big. I did have a frame form the same manufacturer of the same age, and that was 18", and always felt too long. I'll give it a miss.
Ta
I think you mean Big != Too big.
Any opportunity to draw it up in Google SketchUp & compare it to a known quantity?
How do you define too big? As has been said, TT length is more important than seat tube for most of us and they have been getting longer over the years (to go with shorter stems). So an older 20" frame may well have the same TT as a modern 18". As long as you can cope with the standover the longer TT (with shoer stem) seems to work better for most people than a shorter TT and a longer stem.
Why does the standover matter? Genuinely asking this as I have been thinking about this for a while. If the BB height is the same across frame sizes then it only matters when you dismount right?
Yes, particularly if you dismount in a hurry 🙂 Mind you, if I have the sort of crash that sends me forwards it's usually the stem or the rocks a few yards down the trail that get me rather than the top tube.
Stand over infers a lower top tube which gives you space to move around on the bike when yer bustin' yer radical moves 'n' stuff.
Standover also helps with control clearance- ie, at full lock, do your shifters hit the top tube!
What's generally more important imo is the minimum saddle height- couple of mates have bikes with really tall seat tubes (for some reason) and they can't get the saddle down as low as they'd like, limited choice for dropper posts too, bit of a bummer.
