Switching 27.5 to 29. Some calculations.

outerlimits

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Feb 3, 2018
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Found this chart that gives circumference of various wheel Tyre combos.

BikeCalc.com - How to calculate Bicycle Wheel Size

Done the calculations to work out the diameter and radius.

Now I have 27.5 x2.8 and want to change to 29 but what width Tyre ???

I’ll use my calculations below to work out if I got clearance ect.
Size.,, Cir.,, Dia.,, Radius
27.5x2.8,,, 2281.55,,, 726.24,,, 363.12

29x2.6. 2369.01 754.08,,, 377.04
29x2.5. 2353.05 748.99,,, 374.49
29x2.4. 2337.09 743.91,,, 371.95
29x2.35. 2329.11 741.37,,, 370.68
29x2.3. 2321.13 738.83,,, 369.41
29x2.25. 2313.15 736.29,,, 368.14

now I have got approx 20mm frame clearance and want to have approx 10mm clearace.
So a 29x2.5 will leave me with approx 9mm clearance. Also raising the bottom bracket 11.37mm.

Wonder how this would affect the handling of the bike being higher ?

Different brands and treads will measure different, but at least the above will give a bit of an indication when making the swap.

Now I need me some pie
 

Gary

Old Tartan Bollocks
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Firstly. What are your reasons for changing to 29" wheels?
Don't choose tyre width based on ride height or clearance. Choose tyre width based on ride preference and the conditions you ride.
The bike won't handle actaully massively differently. Assuming you'll be running the same size front and rear geometry will remain the same including BB drop whatever width/size tyres you fit. But the tyres/wheels will
Let me explain.
Axle AND BB height will change. this will have 2 effects.
Firstly with a higher axle height and larger diameter wheel a bikes turning characteristics will change slightly. whether you even notice this is another thing altogether.
Secondly the higher BB and axle height will make the bike slightly less stable but give you more pedalling clearance.
When you tip the bike into corners a larger wheel will react slightly differently (slower but with more inertia so also slower to self right). But as you're changing tyre width too this trait may be masked somewhat, especially if your old 27.5x2.8 tyres are heavier than the new 29"ers. Especially if you are changing tyre width, tread and pressures at the same time (Which you will be)Again. I may be wasting your time completely telling you this as for all I may know you may be the type of rider to not even notice.
Basically you're either going find you like it a little more or a little less or after the first few rides not even notice it at all.
It'll all depend on how in tune you are with a bike and it's handling traits in the first place. How skilled a rider/experienced you are, your riding background and how fussy/intune with set-up you are. All of these things will all come into your perception of the change. Along with what I've just told you messing with your head.
Definitely try it if the cost is no shakes to you either way... it's good to try new things and learn to understand how changes affect your ride.

Pie will lower the bike's ride height (sag).

Mmmm... pie

Ps. Finally. Have a look at exactly how much 9mm and 11mm are. In the grand scheme of things the difference you're worrying about is princess and the pea territory.
 
Last edited:

outerlimits

E*POWAH BOSS
Founding Member
Feb 3, 2018
1,241
1,574
Australia
Firstly. What are your reasons for changing to 29" wheels?
Don't choose tyre width based on ride height or clearance. Choose tyre width based on ride preference and the conditions you ride.
The bike won't handle actaully massively differently. Assuming you'll be running the same size front and rear geometry will remain the same including BB drop whatever width/size tyres you fit. But the tyres/wheels will
Let me explain.
Axle AND BB height will change. this will have 2 effects.
Firstly with a higher axle height and larger diameter wheel a bikes turning characteristics will change slightly. whether you even notice this is another thing altogether.
Secondly the higher BB and axle height will make the bike slightly less stable but give you more pedalling clearance.
When you tip the bike into corners a larger wheel will react slightly differently (slower but with more inertia so also slower to self right). But as you're changing tyre width too this trait may be masked somewhat, especially if your old 27.5x2.8 tyres are heavier than the new 29"ers. Especially if you are changing tyre width, tread and pressures at the same time (Which you will be)Again. I may be wasting your time completely telling you this as for all I may know you may be the type of rider to not even notice.
Basically you're either going find you like it a little more or a little less or after the first few rides not even notice it at all.
It'll all depend on how in tune you are with a bike and it's handling traits in the first place. How skilled a rider/experienced you are, your riding background and how fussy/intune with set-up you are. All of these things will all come into your perception of the change. Along with what I've just told you messing with your head.
Definitely try it if the cost is no shakes to you either way... it's good to try new things and learn to understand how changes affect your ride.

Pie will lower the bike's ride height (sag).

Mmmm... pie

Ps. Finally. Have a look at exactly how much 9mm and 11mm are. In the grand scheme of things the difference you're worrying about is princess and the pea territory.

Fairly in tune with the bike. I’d like to make it a bit more nimble and playful in the rear. I don’t want to drop the bb any lower, but higher will help with pedal strikes and motor strikes. I like the way it turns as is, and the rear just hangs on in turns and in a straight line. I don’t mind a bit of drift in the rear however. The front feels heavy and sticks like glue. In slower rocky technical trails, the high volume front seems to ping off things more than I’d like.

A mate has a spare set of 29’s with 2.3, and i’m going to give em a go. He’s up for selling them cheap too. My rear rim has had more hits than Elvis, and looking at replacement options.


Pie will lower sag for sure. Just felt like some after all the pi calculations
 

Gary

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Are we talking about a Levo here?
Levos don't have low BBs
and raising the BB 11mm higher BB isn't going to make it any more playful.
Getting rid of the plus tyres will. trust me on this.
Learn to pre-empt the trail/obsticles using manuals and hopping and time pedal strokes to stop smashing your pedals/motor and rear wheel into things.

Also, What size and weight is the bike and what height/weight are you?
 
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outerlimits

E*POWAH BOSS
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Are we talking about a Levo here?
Levos don't have low BBs
and raising the BB 11mm higher BB isn't going to make it any more playful.
Getting rid of the plus tyres will. trust me on this.
Learn to pre-empt the trail/obsticles using manuals and hopping and time pedal strokes to stop smashing your pedals/motor and rear wheel into things.

Also, What size and weight is the bike and what height/weight are you?
Yep, Levo
Skills are ok at the above mentioned, but it still happens on occasions and it’s a no brainer a higher bb will lessen this.
I could change the rear out for a 2.6 Tyre which will drop the rear approx 5mm and shed a mere 95grams. It will shed more if I go a narrower, lighter spec wheel too.
The bb height may drop approx 3mm, and have slight impact on frame geo.

Just throwing some ideas around.

Bikes a large alloy Levo 22.7kg and I’m 186cm and 115kg with all the kit.
 

Gary

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If your aim is to make the bike more nimble lightening it up (especially the tyres/rims) and going to narrower tyre diameters at high pressures is the easiest way to do so.
Your (I assume) Butcher grid 2.8s will actually be 300g heavier each than the Exo Minion SS/DHFs I run. Tubeless will save a fair bit of weight too if you haven't already but you have to realise it's not just about the weight. the 2.5/2.3s need to be run at firmer pressures and are much more nimble for it. as are faster rolling compounds. and unlike plus tyres a narrower tyre becomes more supportive but not pingy like a higher pressure plus tyre does.
Firming up your suspension and reducing rebound damping (obvs not too much tho) will also make your suspension poppier/livelier and more playful.
 

outerlimits

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You’re so freaking helpful @Gary, I really appreciate it.
3c DHF and DHR dual compound rear combo here.
I don’t really understand your last statement however.
I thought running a faster rebound would liven it up. If I were to up the pressure and leave as is on the rebound it would do the same. Don’t know bout upping pressure and speeding up rebound however. I think that would really make it pop.
 

Gary

Old Tartan Bollocks
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Ok. I'll try and explain better for you. Bear in mind I don't know how you have your suspension set.
What i'm saying is a firmer spring rate will give more support (for when you pump/pre-load the bike to unweight/lift the wheels)
And a faster (but not so fast as to buck or oscilate wildly) rebound setting will give back the pre-loaded energy with a poppier delivery. Don't run your rear rebound faster than the front either. If anything leave it slightly slower than your fork.
Good timing and technique is still key but you can change both of these things to help you get the bike making shapes and changing direcion in the air etc more easily.
You're a fair bit heavier than me and I don't know your strengths etc. either.
Good core strength and fitness help tons with maneovering a heavy Ebike about playfully too, especially if you're a heavier rider (I'm not light BTW, but I am a pretty strong rider)
 
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