GPR tire pressures

[jkv357]

For you daily Derbi/Aprilia street riders -

What tire pressures do you find work best with these light bikes/small tires?

Lower pressure than your "average" cycle tire?

Thanks.


Jay

[kaldis12]

My rear tires had about 3 bar pressure in it. A bit more or less depending on the weather. It was like 3 bar on a warm, sunny day with warm road. About 2.8 bar with cold road.

At the front wheel it was 0.2-0.3 less pressure than in the rear one, depending on the weather.
My bike is 80kg plus me so about 140kg for the whole bike.

[toratora]

There are a lot of depends in this department!

In the morning for the street GPRs I will run around 29PSI. On the track with the GPRs maybe drop down to 19PSI. With the Cobra due to my weight something around 23PSI.

The thing is there are numerous variables. The bike, the tires, the temp, your weight, if the tires are warm or cold, and the location. The thing to do is try different pressures, and see of you notice a difference.

[kaldis12]

Whoa those are pretty small numbers. I'm always unable to drive with such a low pressure

[jkv357]

My rear tires had about 3 bar pressure in it. A bit more or less depending on the weather. It was like 3 bar on a warm, sunny day with warm road. About 2.8 bar with cold road.

At the front wheel it was 0.2-0.3 less pressure than in the rear one, depending on the weather.
My bike is 80kg plus me so about 140kg for the whole bike.

With conversion, that is 43.5 and 40 PSI - is that right?

I'm normally running my street tires in the 32 to 34 PSI range, and had been running the Derbi a bit less - like 28 PSI.

The weather here is in the 50F range lately, and I'm wondering if I should drop a few PSI to get a quicker warm-up.

[toratora]

Whoa those are pretty small numbers. I'm always unable to drive with such a low pressure

Part of this is the tires. I wouldn’t run those pressures on an MC18 at the track. Well I might try it.

The weather here is in the 50F range lately, and I'm wondering if I should drop a few PSI to get a quicker warm-up.

How long do your tires usually take to warm up? Out at the track the Sava slicks are pretty much ready after the sighting lap. The MC18 street tires warm up usually well before there’s any cornering acton going on.

[jkv357]

How long do your tires usually take to warm up? Out at the track the Sava slicks are pretty much ready after the sighting lap. The MC18 street tires warm up usually well before there’s any cornering action going on.

That's hard to say - a while.

I set the tires at 29 PSI in the shop at about 65F, and the temp was about 55F when I left this morning - so they were at about 28 PSI.

They felt fine, but I didn't push it very hard.

It feels like the jetting is very close, and it pulls well on the flats. Uphill is the biggest issue. Some of the hills are long, and even with the required downshifting the speed drops off quickly. I do have a +1 countershaft on it, so that does affect its ability to climb hills.

[toratora]

Sounds like bad tires to me. This is why 17s are so important for these bikes. Getting decent 16" tires has gotten very difficult. With the MC18s I can almost throw the bike into the corners after just starting the bike up. Very quickly they provide a serious amount of confidence. And once you’ve run some corners they provide an insane amount of confidence.

On all of my GPRS if the hill is long enough eventually you’ll have to down shift. This is most noticeable when riding on the freeway.

[jkv357]

Sounds like bad tires to me. This is why 17s are so important for these bikes. Getting decent 16" tires has gotten very difficult. With the MC18s I can almost throw the bike into the corners after just starting the bike up. Very quickly they provide a serious amount of confidence. And once you’ve run some corners they provide an insane amount of confidence.

On all of my GPRS if the hill is long enough eventually you’ll have to down shift. This is most noticeable when riding on the freeway.

The Avons I have on it are acceptable at this point, but nowhere near what a really good tire like a Sava would be. I'm not planning to upgrade to 17s, so I'm stuck.

I haven't run on the freeway for any length of time, but the hills around here are big and long enough that I am downshifting frequently. I'm noticing that 7000 RPMs is really the basement. Anything under that and it's really soft.

What the safe limit for revs on the EBE-075? I usually keep it under 12, and closer to 11 max. I'm running Motul 800 RR at about 40:1.

Thanks!

[toratora]

Yeah I think 12K is the redline on that engine, and there’s not much more power to be found in over revving it. Due to the 43mm rod though it has a bit more torque than the fifties so you can generally run higher gearing on them.