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[Closed] How much influence do tyres (and wheels) have on geometry?

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[#7793594]

So, I changed the tyres on my 26" bike and the BB is 1/4" lower, meaning the head and seat angles will also be slacker.

With such a marked difference, it's in the same league as an angleset or offset bushes.

Could wider rims and the different stance of the tyre on the rim have similar results?


 
Posted : 27/04/2016 12:17 pm
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So, I changed the tyres on my 26" bike and the BB is 1/4" lower, meaning the head and seat angles will also be slacker.

The angles will be the same unless you only put a smaller tyre on the back.


 
Posted : 27/04/2016 12:20 pm
 mboy
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If you've changed both tyres and they're similarly smaller, your angles are the same as they were before but your BB is lower. The angles would only change if you'd fitted a drastically bigger tyre at one end than the other.

You're definitely overthinking this FWIW...


 
Posted : 27/04/2016 12:21 pm
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erm...... if you've lowered the front and rear by the exact same amount then the geometry is identical bar a lower bb


 
Posted : 27/04/2016 12:21 pm
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don't forget the effect of tyre pressures.


 
Posted : 27/04/2016 12:23 pm
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There will be an [s]almost[/s] imperceptible reduction in trail. Angles will be the same.


 
Posted : 27/04/2016 12:23 pm
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The perfect JHJ wheel you can see the conspiracy theory's going round and around for ever.
[img] ?664[/img]


 
Posted : 27/04/2016 12:31 pm
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As above, angles won't have changed if both wheels had different tyres but trail will have changed so it will have a (negligible, IMO) effect on handling.

Makes you think, doesn't it? ๐Ÿ™‚


 
Posted : 27/04/2016 12:35 pm
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I told a little fib...

I changed the back tyre and the wheels; using the same front tyre, but on a different rim; rims are a bit wider (24mm internal over 21mm internal), back tyre is a little smaller (Highroller 2.35 instead of Kenda Nevegal 2.35)

I reckon there's a challenging GCSE maths question in there: Using calculus, what front tyre am I using? Show your workings.

Still surprised that there is that much difference, though I do like having the lowest BB in the county.

Mason hunt eh?

[img] /revision/latest?cb=20140525133914[/img]


 
Posted : 27/04/2016 1:00 pm
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front is a maxxis minion dhf 2.35.


 
Posted : 27/04/2016 2:13 pm
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I see what you did there, unfortunately, you're wrong...


 
Posted : 27/04/2016 10:18 pm
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You wouldn't need calculus. Trig maybe, but not calculus.

Also, calculus is more of an ALevel topic.


 
Posted : 27/04/2016 10:29 pm
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Calculus is a far better word than Trig, rest his soul...

[img] [/img]

Either way, you'd need a pretty extensive knowledge of knobs to work out what I'm rolling on

(There may be a clue in this post)


 
Posted : 27/04/2016 10:44 pm
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I hope this is on a fully rigid bike. I'd hate to think what would happen with 160mm both ends.


 
Posted : 27/04/2016 11:02 pm
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God dammit... Is Trigger dead too?


 
Posted : 27/04/2016 11:35 pm
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Afraid so...

and whatsmore:

I'd hate to think what would happen with 160mm both ends.

Afraid so~ (well 160mm on the Front, 150mm out back)

[b]
12.7" BB[/b]


 
Posted : 28/04/2016 12:38 am