 You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
Trying to compare diameters of 27.5 and 29er wheel/tyre combos to see how switching will affect BB height but the two I have tried both give the same results for each wheel 'standard'??
ie;
650b/2.4 = 60.7
29er/2.4 = 60.7
And so on...
https://www.bikecalc.com/wheel_size_math
http://www.berkshiresports.org/index.php?ID=bikecomputertiresizecalculator
I must be missing something here as the rims are different diameters as we all know and going 29er to 650B or 29 F, 27.5 R will affect BB??
you are looking at the wrong number. 60.7 is the height of the tyre.
29: 743.92
27.5 : 705.92
What a ****ing idiot...what was I thinking 60.7 was anyway? inches I think?!
Note to self: don't look at bike tyre size calculators in a bleary eyed sleepless night state.
Thanks. 🙂
720mm for a 2.5WT 27.5 tyre too, measured on my DHF 2.5, so in between regular 27.5 and 27.5+/29.
I wouldn't trust that method due to two things:
1) It assumes the tyres run true to size and that they're as tall as they are wide.
2) It ignores the fact that when you sit on the bike the tyre height will reduce by perhaps 50%, assuming you're running tubeless at appropriately low pressures.
In reality 29x2.4 tyres are normally a little under 60mm in height, and a 27.5x2.8 around 65mm, based upon various numbers in here:
http://www.reifenbreiten-datenbank.de/reifen.html
So the difference in tyre height is likely to be a little under 10mm, and whatever it is it'll perhaps half once you're actually sat on the bike. And the 27.5 wheels have a radius of 19mm less than 29er's.
So total drop in bb height, moving from 29x2.4 to 27.5x2.8, when actually sat on the bike, is probably around 15mm.
This picture says capture my excess words above much better:
https://forums.mtbr.com/26-27-5-29-plus-bikes/27-5-tire-height-1009036.html#post12585348
Thanks very much for that.
If I went say 29er with either 2.4 or 2.6 tyres to 27.5 with 2.4 or 2.6 tyres (not + size) can you give me the likely height change?
I guess also if trying to see how going to a mix, ie: 29er/27.5 F/R would change things it depends on the wheelbase, chainstay length etc?
If you use the same size tyre at the same pressure with the same internal rim width then changing rim diameter will basically mean the difference in wheel diameter is the difference in rim diameter.
A larger diameter wheel at the front will slacken head and seat angles slightly, increase trail slightly, reduce reach and ETT slightly, increase stack slightly, decrease the wheelbase microscopically, and either raise or lower the BB slightly (depending on whether you started with the larger or smaller diameter wheels). It'll also push your centre of mass back slightly.
Whoops, edited before noticing your reply, sorry...
If I went say 29er with either 2.4 or 2.6 tyres to 27.5 with 2.4 or 2.6 tyres (not + size) can you give me the likely height change?
So you mean just dropping wheel size without changing the tyre size? That would just give a 19mm lower bb, assuming the same model of tyre and rim width.
I guess also if trying to see how going to a mix, ie: 29er/27.5 F/R would change things it depends on the wheelbase, chainstay length etc?
Ah, I've been running mixed set-ups for ages. Yes the ratio of wheelbase to chainstay length would affect things a bit, but probably not that much. What are you planning to do and what bie do you have?
In any case, it's very easy to over-think these things.
(Although things can go wrong. I once built a 26er jump bike from I was a young teen and put 24" wheels on it. My toes hit the ground on corners, it was basically unrideable.)
Understood - just not sure how a typical 2.4 fared on the 27.5 rim vs 29er given that (IIRC) plus tyres had a higher profile (ie taller as well as wider) and not sure if the newer 2.6ish (plus-lite??) were affected too?
As noted only thing is to try it but just aiming to get an idea.