I had a set of 2.3" Maxxis Minions on my DH bike. They have about had it so I went on the Wiggle site and bought a paid of 2.4" Panaracer Fire FRs.

Panaracers arrived nice and quickly. Fitted them today, but the front one catches on the ofrks and the rear on both the frame and the front mech. There was plenty of room around the old Minions.

I noticed some time ago that my 1.8" Tioga XC SLs appear to be much smaller than my 1.8" Panaracer Fire XC Pros, and that my 1.95" IRC Mythos and 2.1" Schwalbe Racing Ralphs and Nobby Nics all appear to be about the same size. My 2.3" Conti Speed Kings look even smaller than the Minions.

Why the discrepancies, do some manufacturers not nclude the depth of tread when quoting sizes? The blocks on the Fire FRs are huge. Is there any sort of 'official' measurement? If I buy tyres I am unfamiliar with instead of Fire FRs, say some Nokians for example, what size would be the same as a 2.3" Maxxis and how would I know?

I know rim width can affect tyre shape and depth, but the Maxxis and new Panaracers were on the same rims.

It is just random irritating bull**** as far sa I can tell.

If you want to keep things simple, Kenda invested some of their R&D budget in a ruler, and every monday * John Tomac himself drops by the factory and measures every last tyre. If they turn out to be randomly mis-sized, he puts a Continental sticker on them instead.

(* except bank holidays, when Eric Carter has to do it)

That story might not be entirely true, but Kenda do own a ruler.

About time for a proper standard on this one. I know we have the ERTRO thing, but really, what we want is to know that one manufacturers 2.1 or 2.3 is the same as any other manufacturers.
For what it's worth, Panaracer are generally about right with sizes, Conti come up small for a given size and Maxxis depends what you buy. The Advantage, Ardent etc in the new 2.25 are bigger than the Minion, high Roller etc 2.35. A 2.1 Aspen is bigger than a 2.1 high roller. New range sizes come up bigger than old range sizes. Hutchinson seem about right on sizes too.

I'm sure MBUK tried it about 1,000,000 years ago. They called it STAR (standard tire and rim). They measured everything on a mavic 317 at 40 psi and cave the carcass width followed by the tread width. Even Bontrager Tyres did it for a little while when they first started making mtb tyres. Not sure why it died out (other than it was linked to MBUK).

Anyone else remember that or have I just had another of my funny turns?

Yes we definitely need some kind of standardisation, but one problem is that a tyre probably varies considerably in inflated size depending on rim width

That STAR thing sounds like a good idea.

Even if not everyone uses a 317 and 40psi (and there might be some people who don't) it will at least give an idea of relative size. Eg. tyre A and B are both 2.1 but B is a bit larger, same size as a 2.2 tyre C.

"Yes we definitely need some kind of standardisation, but one problem is that a tyre probably varies considerably in inflated size depending on rim width "

That's true, though not as much as you might expect, in my experience- not enough to explain the wild variations on the market.

What really maddens me is when a brand isn't even consistent within its own ranges. Conti for instance, the 2.2 Rubber Queen is wider than the 2.4 Mountain King for example, that's just nuts.

(I'm told that Conti's standard is to measure the tyre while not on the rim, from side to side across the treaded area, which may not may not be true but certainly is mad, and could explain why their sizes make no sense)

Depends hwo they measure it.

What DH bike can't run a 2.4" tyre? come to think of it, what DH bike has a front mech?

I don't think any kind of tyre sizing standardisation is required at all but when it comes to fitting apropriate tyres it does seem for most on here that common sense is a sadly lacking requirement though.

My 'DH' bike is a bit Retro. Might not even be a proper DH bike to some on here.

Got a coil sprung Marin Attack Trail, 5" of bounce (that was quite a bit back in 1999). RST Hi5 forks, 205mm Hope C2s, World Force risers, but being an XC racer I like to pedal the uphill bits too and not wimp out and get a lift on the tractor, so I have a triple chainset.

Just got another set of Minions (which I notice are actually claiming to be 2.35") and they fit fine. Full marks to Wiggle for easy returns and replacements.