BIG TIRES ON SMALL WHEELS – 650BX42C
The idea for Slate started with the realization that 650b road wheels with massive 42c tires offer the same rollout (outer diameter) as a 700x22c wheel/tire combo. That means we could get the unreal cornering grip and float of big tires, with proper road bike speed and crazy-good handling

Does that mean, I can get some 650B wheels for my gravel/gnar/cx bike, add 42c tires to it and run it like the Slate or is it all a marketing gimmick

Yes you can. Randonneurs have been using 650B for decades, it’s nothing new. It feels different to 700c since there’s no point using the 650×40-odd c unless you drop the pressures, then for all the reasons bigger tyres on MTBs work well, these work well on road and dirt tracks.
Popping the 650B wheels on a bike designed for 700C changes the handling a little, there’s more to handling than just the outside diameter of the wheel, but that’s not to say it’s a bad change or a major difference.

or is it all a marketing gimmick

There is a big element of marketing gimmick in there but I see why they have tried it. I used up to 47c tyres on 700c wheels on a CX bike a few years back. It felt better off road for grip and comfort but it felt a bit more sluggish (bit that was probably just the weight of the larger tyre)
Whether a 650b with a 47c would feel much different would be good to test both back to back.

What size tyres are you running now?

^ After having an off on the road doing a u-turn in tropical down pour, I am back to my Marathon Plus 38x700c until the last of the rains are over.

Top tip – Vittoria Cross XN – great tires in the dry, on hard back, make you fall off in the rain on a wet road though. Almost as if I hit black ice.

There is a big element of marketing gimmick in there but I see why they have tried it

More like the last 40+ years of pushing super skinny ‘race’ tyres for non racers being the gimmick.

650B x big (and other bigger volume tyre sizes) was how it was done before everyone got obsessed with super skinny tyres on bikes not used for racing.

Skinny high pressure tyres have their place (super smooth road and on the track) but for normal riding on less than perfect roads and a bit of rustic tracks then big volume supple carcass* tyres have always been the best way to do it, it just seems that we and the industry forgot that for a while.

If you want to do some reading look up (french) randonneur bikes, and the current customer builders (mostly US) that have been dabbling with them again, and 700c -> 650B conversions, and if you can deal with the slightly preachy nature of Bicycle Quarterly it’s worth a read, there’s some sound reasoning discussed in there (along with a lot of forceful opinion!)

Of course you can do the same with bigger 700C tyres, but the issues then start to be clearance on existing frames and some sluggishness of big 700C wheels with big tyres.

*this is a key point, don’t go comparing heavy duty thick tyres like most MTB slicks or ‘armoured’ touring and urban tyres, but light weight flexible big volume is faster and more comfy on anything other than super smooth surfaces.

Seems a bit of a confused message given the slate has a front suspension as well.

Seems a bit of a confused message given the slate has a front suspension as well.

not a lot of bounce, and imagine the tak on it is big tyres for comfort and small bump/buzz compliance, and a wee bit of boing for hitting big things when offroad.

It’s Cannondale – they specialize in marketing gimmicks.

Run 40c 700c tires on my tripster and they is excellent – but I don’t touch the tarmac if I can help it.

Quirrel – Member

Top tip – Vittoria Cross XN – great tires in the dry, on hard back, make you fall off in the rain on a wet road though. Almost as if I hit black ice.

Mine are about to be sold off in a garage clearout for the same reason, one minute I was riding along at 20mph, the next skidding on my ass towards a double decker bus

Mine are about to be sold off in a garage clearout for the same reason, one minute I was riding along at 20mph, the next skidding on my ass towards a double decker bus

Worthy of a killer tyres thread – I’ve had some good speed up on mine, glad I never tested out the wet ability at speed.

*this is a key point, don’t go comparing heavy duty thick tyres like most MTB slicks or ‘armoured’ touring and urban tyres, but light weight flexible big volume is faster and more comfy on anything other than super smooth surfaces.

Is anyone doing these with puncture protection? Ive ran Grand Bois Cypres before (700 x 32 i think) and while they were comfy and quick, they punctured a lot more than any other road tyre ive used before or since. The larger footprint of the softer tyre just seemed to pick up debris and it then worked through the very thin carcass.

28mm GP4 seasons are not as comfortable but at least i can do a whole ride without having to stop.

Ive ran Grand Bois Cypres before (700 x 32 i think) and while they were comfy and quick, they punctured a lot more than any other road tyre ive used before or since. The larger footprint of the softer tyre just seemed to pick up debris and it then worked through the very thin carcass.

Not dismissing your experience, but that is the exact opposite of mine with compass/GB tyres.

I’ve found larger lower pressure flexible tyres to puncture a lot less than smaller higher pressure tyres. They seem to deform over a lot more ‘stuff’ when on the road, I’ve been hit a few broken glass patches and winced only to come out the other side OK, I’ve not noticed them picking up much debris yet, but then I’ve been using the slightly different treaded Compass variants rather than GB, not sure if that would make any difference to how much they collect?

In fact the only puncture I’ve had on 38c Compass’s has been when I hit a big pointy rock on a quarry road descent (offroad) while heavily laden and not looking where I was going, pinched it good and proper but I probably would have pinched and MTB tyre with that impact too, and to be fair to them I’ve only put about 1200 miles on the Compass tyres so far.

I had similar experience with a set of Michelin Wild Run’R tyres on some 26 inch wheels, nice and flexible, ran at about 35/45PSI for ~2,000 miles and no punctures and did a lot of laden towing with them, they’re still in good nick but the bike they were on has moved on.

Paranracer (who make the Compass and I believe the ‘Dale tyres too) still do the Pasela, which although not as light/flexible as the extra-light Compass carcass are still very good, and they have both a thicker tread and some puncture protection. Pretty good compromise option.

I get a similar effect on skinnier road tyres actually, 25c Ultremos (nice and thin/flexible) seem to deform more and not collect debris, where as thicker puncture protected Bonty Hardcases pick up all sorts of stuff, it’s all stuck in the tread and hasn’t made it through the carcass though so I guess they’re doing their job, but I can’t help but think that a more flexible lighter tyre wouldn’t have collected it in the first place.

Tyres, and especially puncture experience is always very subjective and dependant on conditions though so hard to state anything as fact vs opinion.

I should clarify my experience a little better, may have been harsh with my last comment. I have had quite a lot of punctures with them, cant say how many per mile (as it was a few years ago) but within the 1 per 100mile region, certainly on a C2C ride there were 2 punctures with them (and felt ‘expected’ based on previous use). It was mostly road grit/dirt that was the cause, not really problems with gravel or rocky tracks.

For comparison my next ‘most punctured’ road tyre would be a Vittoria corsa CX 23mm which punctured about once every thousand miles.

but within the 1 per 100mile region

that would annoy me too!

but I’ve certainly not had anything like that from any tyre on a regular basis.

Stato, same here. Supple casings feel great but I got fed up with the number of flats. Now using panaracer gravel kings on one bike, much better. Less supple but at 5-8psi less than the more supple lighter casing tyres they feel great.

panaracer gravel kings

I’ve got a pair of these ready to try out at some point too as they piqued my interest. Not had a chance yet though but good to hear some first hand feedback.

The 32c ones looked a bit more aggressive on the tread than I wanted though so went for the 28c ones to see how they fare as a halfway house.

big volume supple carcass* tyres have always been the best way to do it, it just seems that we and the industry forgot that for a while.

I keep reading reviews/manufacturers blurb talking about “massive tyre clearance” on road bikes, then you look at the spec and realise that “massive” means up to 28mm, unless you want guards, in which case it’s 25mm. 🙄

I keep reading reviews/manufacturers blurb talking about “massive tyre clearance” on road bikes, then you look at the spec and realise that “massive” means up to 28mm, unless you want guards, in which case it’s 25mm.

Your reading about race bikes, not gnarmac/gravel/all-road bikes. This new breed are touring tyre sized, but with the intention of thinner casings and lighter loads, so more comfort from tyre (and frames) but still the same speed as a ‘race’ bike.

Amedias, I’ve got the gravel king 42×650, replaced pari motos. Agree with your experience that the lower pressure large tyres deform around a lot of the debris but they still flatted more than once per 100 miles, thorns and tiny flints mainly, more than anything else I’ve used apart from cx contis during hedge cutting season.