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PostPosted: Fri Nov 23, 2007 12:07 pm 
King of the DuckBoard
King of the DuckBoard

Joined: Sun Jan 28, 2007 12:30 pm
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messiah wrote:
I used to run a Campag Atek rim on the front and a Mavic M231? on the rear.

The Campag is non eyelet and very light while the rear was a little heavier and had eyelets to handle the extra stresses - that was my thinking at the time anyway.

Matching rims/tyres etc has never bothered me although I would always go for silver - hard/dark anodised rims never lasted as long for me - they tended to split at the sidewall earlier than silver rims


My thought too. But is their really a difference between silver rims and ano rims? I thought the ano was just for different colour


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PostPosted: Fri Nov 23, 2007 12:36 pm 
Old School Grand Master

Joined: Wed Jun 29, 2005 11:18 am
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Location: near cwmcarn
tintin40 wrote:
messiah wrote:
I used to run a Campag Atek rim on the front and a Mavic M231? on the rear.

The Campag is non eyelet and very light while the rear was a little heavier and had eyelets to handle the extra stresses - that was my thinking at the time anyway.

Matching rims/tyres etc has never bothered me although I would always go for silver - hard/dark anodised rims never lasted as long for me - they tended to split at the sidewall earlier than silver rims


My thought too. But is their really a difference between silver rims and ano rims? I thought the ano was just for different colour


its also a surface hardening treatment, quite a good article below about the pros & cons :)
http://www.bikepro.com/products/rims/rimover.html


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PostPosted: Fri Nov 23, 2007 12:42 pm 
BoTM Winner
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Joined: Thu Jan 19, 2006 1:23 pm
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Location: NW England
Usually run a lighter rim on the front on my hardtail, 519 front 521 rear, and matching rims on a full susser. My thinking is that on a hardtail the rear gets a lot more abuse as you plow through stuff with the front suspension. Would go with matching rims on a fully rigid by the same logic.


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PostPosted: Fri Nov 23, 2007 4:01 pm 
BoTM Winner / retrobike rider
BoTM Winner / retrobike rider
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I run my lightest wheels (Matrix Mt Aero and Bullseyes) on my fully rigid bike and my heaviest/strongest (XT & Mavic D521) on my Klein!

For go anywhere, do anything reliability you cannot beat well built 32h, 3x spokes with any reasonable hub/rim combo. The weight saving of 28holes just ain't worth it IMO.

Just like a great frame - wheel strength comes as much from the build as the components.


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PostPosted: Fri Nov 23, 2007 5:39 pm 
retrobike rider
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Hadn't occured to me before, but wouldn't it be logical for those who run a bigger tyre on the front than the back to run a wider rim as well? I know '2.3' tyres aren't really 2.3" wide, but even so 2.3" is 58mm which makes a 17mm wide 517 sound a bit feeble.

On cars, the rule is that the wider the rim the better the roadholding and people run rims anything up to 90% of the width of the tyre, so that the rim and the tyre have a really unified shape and work together. I'm not clear why we don't do something more like that in mtb.


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PostPosted: Fri Nov 23, 2007 5:45 pm 
Gold Trader
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The reason, as far as I am aware, for the popularity of the narrow section rim is:

1- keeps the tyre profile round, car tyres are usually flat on the ground at all times.
2- lighter, rotating weight is the enemy
3- Keith Bontrager 'invented' (note use of inverted commas) by using 36H Road rims and cutting and re joining them to make 26" diameter 32H rims. He is quite smart when it comes to bike stuff, so I'm confident to go allong with him on this. :wink:


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PostPosted: Fri Nov 23, 2007 6:16 pm 
retrobike rider
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Stick Legs wrote:
The reason, as far as I am aware, for the popularity of the narrow section rim is:

1- keeps the tyre profile round, car tyres are usually flat on the ground at all times.
2- lighter, rotating weight is the enemy
3- Keith Bontrager 'invented' (note use of inverted commas) by using 36H Road rims and cutting and re joining them to make 26" diameter 32H rims. He is quite smart when it comes to bike stuff, so I'm confident to go allong with him on this. :wink:


Yes I see that, but car tyres are subject to lateral forces in cornering just as mtb tyres are, but the logic they use is to keep the sidewalls as straight (and short) as possible, to maintain the shape of the tyre under lateral forces and keep the contact patch on the road. The kind of lollipop shape we use in mtb is much more subject to deformation of shape, and even to the tyre getting ripped off the rim.

Doubtless, as you say, greater minds than mine have decided it, but I wasn't looking for heavy rims - I have in mind say a 30mm xc rim, with shallow, curved, relatively thin sides, blending into the shape of the tyre (I'm thinking disc-specific of course). The greater rim width means you could run a smaller, lighter tyre, but still retain a good contact patch and the same air volume as you get with a small rim and a big tyre - but the reduction in tyre deformation should give you better grip. The same principle works on cars, just trying to figure out why it wouldn't work in mtb.


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PostPosted: Fri Nov 23, 2007 6:20 pm 
retrobike rider / Gold Trader
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on a bike you lean over into corners - a rounded tyre profile is better than a square one for that.


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PostPosted: Sat Nov 24, 2007 2:29 pm 
retrobike rider
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cce wrote:
on a bike you lean over into corners - a rounded tyre profile is better than a square one for that.


Yes, I realise that, but I think the knobs do the work in cornering and my theory is that they need to be on a stable carcass to do the job properly – if the carcass distends in shape, the knobs don’t get a proper chance to grip, as with car tyres.

And I must say while I share the admiration for Keith Bontrager as an extremely knowledgeable guy, I do find mtb a bit of a cottage industry where worthy but not all that highly-qualified pioneers seem to drive design in a way that you don’t find in automotive design, where it’s mega-qualified scientists and technologists that drive development.


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PostPosted: Sat Nov 24, 2007 3:04 pm 
Gold Trader
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You appear to be talking about road cars.
Road bikes tend to use rims a similar width to the tyre, and by running them at high pressures maintain the carcass shape.

Off road bikes use 'balloon' tyres to allow the tread pattern to conform to the contours of the terrain on which it is running, thereby increacing traction, and spreading the weight over the greatest surface area possible.

Off road vehicles also use this principle.

Tyre design for bikes is a big industry, and some very clever people have looked at it. Many of the comapnies that make our bike tyres are big into other areas of the tyre industry. Hardly a cottage industry!

It is silly to compare car tyre design and bike tyre design, they preform very very differing functions. A car tyre does not have to work through a 90 degree axis of camber angle for a start!

Motocross bikes use narrower rims than the tyre width to give a rounded profile and to put the largest number of tread blocks on the dirt as the bike leans over.

If you want to try your idea out then I suggest some Halo Trials rims, and a 2" tyre and see if there is an improvment, just because the majority say it is right don't make it so. :D


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