Rims Question

Anthony":lf4aw3ig said:

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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I beg to differ:
Colin Chapman, William Lyons, Enzo Ferrari, Ettore Bugatti, ******* Shelby, Dan Gurney, Ferdiand (and Butzi and Ferry) Porsche, Paul Roesch.

To name but a few, individuals who drove the design and engineering of the motorcar forward in leaps and bounds, by behaving in a way very familiar to bike fans. By experimenting, going over the managments heads in some cases, using racing budgets for R&D and by just plain cheating. Some were engineers, some (in the case of William Lyons) were excellent sales men, some were enthusiastic ameturs. Not many of them are 'mega qualifed'!

Stick Legs":2ztvqn9t said:

I beg to differ:
Colin Chapman, William Lyons, Enzo Ferrari, Ettore Bugatti, ******* Shelby, Dan Gurney, Ferdiand (and Butzi and Ferry) Porsche, Paul Roesch.

To name but a few, individuals who drove the design and engineering of the motorcar forward in leaps and bounds, by behaving in a way very familiar to bike fans. By experimenting, going over the managments heads in some cases, using racing budgets for R&D and by just plain cheating. Some were engineers, some (in the case of William Lyons) were excellent sales men, some were enthusiastic ameturs. Not many of them are 'mega qualifed'!

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Yes, but all these great instinct guys pre-dated the computer age, when standards were hugely lower than they are now. Enzo Ferrari was so technology-averse that he lost championships he should have won, rather than give up his precious drum brakes, live rear axles, leaf springs, front engines etc etc.

I'm just saying that tyre technology doesn't seem to have moved on in mtb as it has in cars. Have you ever driven a car with cross-ply tyres? That's when retro gets really frightening! I just think that mtb technology in general is a bit of a cottage industry, and there may be advances that could be made but just not the size of market to justify the cost of the necessary research and development.

I don't think MTB tyre technology is that far behind the times.
You need to be comparing mountain bike tyres to motor bikes, (crossers and enduros) where a wide tyre in comparison to rim is common practice, not road cars. :?

...and cross plys are still common for off road tyres.

There are other factors to consider for off road tyres. a tall side wall and rim protection for a start. you can then run lower pressures to get more grip. Off road tyres (truck or bike) tend to have tread further up the sidewalls too to grip in softer conditions and bikes lean over in corners when F1 cars don't.

I know a fair bit about cars...

... and some of it might just translate.

If you think of the combination of tyre and suspension as the total suspension system, its job is to be a low pass filter. The buzz and bumps of the terrain should be evened out, in order for the "signal" of terrain changes to come through loud and clear to the rider and for rider inputs to be played back to the contact patches in the same way, whether they be steering, acceleration or braking.

The essence of the job of the tyre/suspension is this frequency dependent filtration. The tyre's job is to take out the higher frequencies (of small amplitude); the suspension takes out the slightly slower frequencies which tend to include bigger amplitudes. The grip you experience is partly a function of the contact surfaces (tyre tread appropriate to the ground conditions, with a contact patch shape determined by pressure and load) but is a large part influenced by the frequency response of the tyre and suspension (legs/arms too with a skilled rider out of the saddle). You want the suspension and tyre to work in partnership with a gradual handover of response as input frequency varies.

This is why running a big balloon tyre on a narrow rim with a racy, taut suspension setup is a nonsense; the suspension will fight the tyre to aborv the same range of frequencies.

This is why a 1.85in Smoke Lite Comp run at 55 psi with a 6 inch travel all mountain rig will not work right; there is no chance that the performance of the tyre will neatly handover to the suspension, leaving you with a bunch of frequencies that are unhandled (grip will probably be poor).

Because MTBers are independent-minded types and everyone seeks out their own sweet spot, you do get wildly varying advice on tyres/rims/pressures/suspension. I try to stick to the principle of keeping all components in proportion. If I am setting up a racy bike, the suspension will be firmer and have less travel; the tyres will be smaller; they will sit comfortably on a narrower rim. If I am setting up an all mountain bike, the tyre suspension and rim will all be proportionately larger and the speed of response of the ride will be lower.

All of this is of course complicated by the other significant factor in suspension calculations... the sprung mass. Rider mass over each axle varies hugely just through body position changes, without even considering variations between riders. If you have a hardtail, one end of the bike is going to be chasing radically different frequency responses to the other end. This all represents fantastic, challenging arena in which to constantly play with setup, with self-delusion telling you whether or not you've got the answer right.

Well after reading the views from you good people. Plus as nobody wants my NOS campy rims. I'm having Ateks on the front of two bikes, One with a rasta Bulllseye hub and one with a silver hope ultra light. Should look good on the yellow Trimble & black Trimble.
I've found the discussion very interesting on the subject also. If not maybe a little off topic
But always an education being on the site

I can't recommend the Atek for rim brakes (except perhaps parallel linkage brakes). The rim shape falls away from the brake pads as they actuate. Brake adjustment is very difficult and minor brake wear results in the pads slipping off the rims. Feels rubbish at the lever too.

I have (within arm's reach) the Atek I trashed into a tree in 1993. I have its intended replacement here too... a Mavic 230 SBP (I have a pair, never built up). The Mavic is the same weight, is eyeletted and has a much better shape for rim brakes.

As i've already bought these Ateks. And i can only buy when i sell other kit. The Ateks it is. Also i ran Ateks on my 93 Klein with no problems. I like Mavic rims. But considering i dented a 717 rear at the peaks i'm not that keen on 07 rims. I'm not a heavy rider and not a mad down hiller. I should not have dented a 717. Oh i wanted 28 silver rims. But couldn't lay my hands on just one. The LBS could only get 717 in black ano.
So will just have too use what i have. Two highly polished Atek 28 silver.

I guess I'll have to build up my 230s on my M900 hubs then (complete with titanium axles and titanium bolts that never worked too well on suspension, but now I'm back to rigid, work fine...). Honestly, I'm not kidding. I've had this stuff sitting around for years and it really looks like its time is come.