SuperMoto Junkie banner

1 - 12 of 12 Posts

·
Registered
Joined
·
212 Posts
Discussion Starter #1
I read this on the tips section

"All '02 and older TTR's, and newer standard and "L" models without the aluminum swingarm, are restricted to a 2.75/17" rear rim with a 110/70 tire. The '03 and newer "LE" models with the wider aluminum swingarm have the choice between the 2.75/17", or the prefered 125GP sized 3.5/17", rear rims. The 3.5" wide rear rim allows you to run tires up to a 120/70 without any issues. 120/70 is the most common size of sportbike front tire, and they work great as rears if turned backwards. High performance street tires, DOT race tires, and full blown slicks are all available. "

My question is this, why do you have to run the 120/70 rear tire backwards?

I have the 2.75 front and 3.5 rear rim. What is the best tire, for those of you that have tested them, for supermoto. This is for a 10 yr old on a TTR. Thanks for the input.
 

·
Registered
Joined
·
5,434 Posts
I am running 125GP tires on TTR with 2.5 x 17 on the front and 3.5 x 17 on the rear. They fit perfect! They will def. work with your rim size. If you want real race tires 125GP are the only real choice with such small rims.
 

·
Registered
Joined
·
1,254 Posts
Hey johnny,
I know that a lot of riders run the tires both directions. It really doesn't make a difference. Most guys will reverse the tire to wear the other side.
 

·
Registered
Joined
·
1,310 Posts
jnybbad said:
My question is this, why do you have to run the 120/70 rear tire backwards?
Bad Johnny Dad,
I'm not a tire pro, but I believe the answer is in the carcass of the tire. the cords are lined up in the tire to be put under a load in one direction. The front wheel is designed to be on a 400lb race bike going 170mph. On the other hand, the rear tire of a 150hp bike is designed to take a load (imagine a drag tire rippling just at the start of a race) the other way. There is hardly any braking forces compared to the acceleration on the rear. If you are trying to design a tire with the lightest weight, you are only going to re-inforce what you need.

Now, all that said, your 90lb son on a 160lb bike going 30mph will be fine with the tire turned either way. Your son will most likely never develop the proper heat in the tire (starts at about 170 F) to reach optimum grip. If you're going to go with the 120 front on the rear idea, you might as well find a street oriented performance tire because they heat up quicker and have a lower optimum grip tempature.

If you want the winning ticket, buy a new set of 125gp rain tires. They will probably last all season, they'll work sweet in the dirt, and they'll be super sticky right out of the gate. The problem is cost and availability. Try $300+ for a set, and you have to go to a race tire vendor to get them.

I found mine by hanging around the pits at a roadrace and asking the 125 guys for take-offs. $50 for a set of slicks and $100 for rains.
BTW, I found a guy that has a whole bunch of used take-offs, and he's working on a list of inventory for me right now. Once I know more, PM me and I'll hook you up.

Hope that helps,
Kevin
 

·
Registered
Joined
·
419 Posts
Go with thw 125 gp tires. I did and they performed great at my track day last weekend. I bought Bridgestones from Bare Bones racing and they were $260 for the set. You will not be disappointed!!
 

·
Registered
Joined
·
890 Posts
jnybbad said:
I read this on the tips section

"All '02 and older TTR's, and newer standard and "L" models without the aluminum swingarm, are restricted to a 2.75/17" rear rim with a 110/70 tire. The '03 and newer "LE" models with the wider aluminum swingarm have the choice between the 2.75/17", or the prefered 125GP sized 3.5/17", rear rims. The 3.5" wide rear rim allows you to run tires up to a 120/70 without any issues. 120/70 is the most common size of sportbike front tire, and they work great as rears if turned backwards. High performance street tires, DOT race tires, and full blown slicks are all available. "

My question is this, why do you have to run the 120/70 rear tire backwards?

I have the 2.75 front and 3.5 rear rim. What is the best tire, for those of you that have tested them, for supermoto. This is for a 10 yr old on a TTR. Thanks for the input.
I can assure you from experience that a TTR 125 will run as fast on a 2.5x17 front and rear as ANY rim set up. Mount a 95/17 front and a 115/17 rear. Just my .02. Cam
 

·
Registered
Joined
·
212 Posts
Discussion Starter #8
Well I ended up keeping the 2.75 front and 3.5 rear rim set up. I put 110/70/17 front and 120/17/rear Michalin Pilot Race tires on. He loved it and had no problem with traction. I guess maybe as he get faster and knows how to feel a problem we can see about a different rim and some slicks. He just rides through the problems now and comes in with a huge smile on his face and tells me everything feels good.

For his first time out I was really impressed. I know I am a little biased but he was passing everywhere and dragging his peg through a number of turns!! I think the 125 youth class may have a little new competition this year.

See you guys out there!!
 

·
Registered
Joined
·
4 Posts
I am running 125GP tires on TTR with 2.5 x 17 on the front and 3.5 x 17 on the rear. They fit perfect! They will def. work with your rim size. If you want real race tires 125GP are the only real choice with such small rims.
I realize this is an old post but... i'm setting up a ttr with 2.75 front 3.5 rear. when you say 125gp are you running two front tires 120/70/17 the same size front and rear? whats the biggest tire you can run in the back? 120/70/17? when i measure it looks to be the 120, mabey the 125/ I wuld like to run a 110 in the front. thanks for the help.
 
1 - 12 of 12 Posts
Top