A forum for owners of Yamaha TTR250 trail and enduro bikes!

I asked Robin about the tyres and have copied his reply below. Many thanks for taking the time to write it up Robin if you read this!

Hope you can handle the tyre nerdery Simon - you did ask 

Hi Brian,

Errr how much tyre nerdery can you handle?!

Bike arrived back yesterday from USA.

Think the ship took a very cold route as fuel lines are hard and shrunk. Also the decompressor plug is leaking as though it has shrunk.

Actually in the states the carb was leaking for the first week and it took me a while to figure out that it was the tiny o rings (which I had not replaced when replacing the main carb gasket) which were leaking due to being frozen at 36 thousand feet and shrinking enough to drip. Got better with heat down in Arizona.

Anyway, tyres.

The rear has 8 to 9mm left on the centre knobs (15mm new). That’s after 4000 miles. Maybe 1000 of which were gravel/off road.

I reckon they would be good for 8 to 10 k miles total on a lightly loaded bike.

You need to watch pressures with temp/ altitude. The centre carcass has a lot of flex (front and rear), so I run 25 psi on roads other wise it would increase wear with the flexing. Its probably due to the tyre originally being the Trelleborg army special that mitas bought up. The Swedish army used them on their bikes and it probably is the best snow/ cold-weather tyre before getting onto studs.

I ran tubeless rear with a bit of slime and HD tube plus two rim locks on the front.  

Rear rim width was 3’’, front was 2.15’’.

The width worked well for all surfaces except for very spirited leaning over on roads, where you find the edge :/ Or rather the side walls are stiff but the edge knobs have a bit of flex which is disconcerting. Reckon the best rim would be a 2.50 or 2.75. the wider rims mean more surface area contact which spreads the load = longer wear and not just the centre of the tyre wearing out.

My most recent favourite (but not long term tested) is the Sava Rockrider 120/80 18 on a 3 inch rim. Stiffer carcass than 644 but will still compress with less psi for the all important bigger footprint in the sand.

After trying all sorts of bigger fatter tyres eg. Mich desert, Dunlop 908RR, mich desert race and more I finally am coming back to smaller tyres. Those rally raid tyres are really for heavier bikes. Plus the actual tyre is heavy and think slower as the motor has to turn the thing. And though looks good you need to adjust the gearing too. Also you need to remove the chain guard to fit a 140 section rear tyre on. Plus even add a link on the chain. Removing the guard means higher chain and sprocket wear from the dirt thrown around.

It’s funny but after much experimentation I am arriving back at mostly stock settings! Eg. 14 front and 44 rear sprockets. And a 120/80 rear tyre. 3’’ tubeless rear is def good though for long distance self supported adventure travel.

Fyi a Dunlop 908RR weighs 17 lbs where as the 644 is 13lbs and the rockrider MC23 is 11.5 lbs.

The Sava MC23 also has a higher speed rating too but not a really an issue for a TTR. (Mitas 644 is 81mph tested).

For the front the 644 is still the tyre I think. Its the biggest fattest tyre I can find. With firm side walls and soft centre it can ride up the side of your house like a Gecko.

The knob pattern means long life. Eg it has off two off-centre centre knobs. Hard to describe. But most dual sport tyres like the TKC 80 or Pirelli mt21 have centre knobs that alternate between one and two knobs. = ok off-road but wears out on the road. And not always how you think. It’s usually the two knobs that wear out before the one. I had to find a replacement tyre after only 4000 mostly road miles when the mc21 wore out every other knob, coast to USA coast.   

I can feel you glazing over.

644 is a great front adventure tyre. Must take great care to fit it right. It often seems seated but isn’t, resulting in uneven/ too fast wear. Again after about 4000 miles in the kalahari this time. Finding tyres was not poss till back in South Africa.

Anyway, enough.

There’s more and feel free to ask but I feel I'm overloading with info.

I still mean to write up the ultimate set up one day.

Oh and the rear lowering link plus fat 644 front makes for great sand riding ergonomics when you want to lean back and surf the bike along.

Hope this helps

-R

LoopSoosStroop wrote:

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Anyone know how many km's he has on his 325 by now?

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 17k miles so far - not bad eh?

TTRfan wrote:

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LoopSoosStroop wrote:

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Anyone know how many km's he has on his 325 by now?

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 17k miles so far - not bad eh?

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That sounds good. I'm always skeptic with upgrades like this, especially considering the reliability of a stock TTR.