Blistering Mojo Tires

Fist time running Mojo’s (softs) for the Rotax series. I keep folding over the soft sidewalls on the rears during high-G corners and I think that action is blistering the inside shoulder-. Running around 8.5 to 9 psi currently, going any higher to support the side walls and they are cooked in 8-10 laps. I’ve have yet to babies tires like this. Swap over to a used set of LeVanto and it was day and night how hard I could get after it and shaved a significant chunk of time. The LeVanto were more akin to the MGs I’m use to running.

Anyone else experience this? Is it just me or do you have to softly load the tires to keep them in one-piece? Thanks

I ran Rotax with Mojos but it was in 2014, I think the compound was D3. They were not a fun tire. You had to sort of baby them and not slide the tire at all. I would characterize it as precise driving, right at the edge of sliding but not over. A bit too much oversteer or a brake lock-up in just one corner would cause the tire to get greasy and lose grip and slow down. The tire would come back by under driving a lap. When track temp was decent, I’m guessing over 100 to 110 F, I’d be running the OTK MXC wheels. Tire pressure maybe as low as 9 but I might have run closer to 10 or 11 but I don’t remember.

I’ve run the PKRA track several times, it’s one of my favorites.

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Which mojo are you running? D5? I’m never able to run lower than 11.5

Do you get to choose your tyres?

This is what I’m finding that it takes a lap to a lap and a half to get them back working which will be difficult in a race. Currently running MXJs since MXCs are so hard to get, but should have a set for race weekend.

Correct. D5s and that is the mandatory tire. Anything over 10psi and tires are toast in 10 laps. Drop pressures to reduce the heat and the sidewalls start working hard also overheating the tire.

I’ve never had any issues with the D5, although maybe correct in having to baby them a bit I never noticed, that’s how I drive anyhow hahaha. I tried 9 psi once it was horrid.

Made some setup tweaks and worked on the loose nut behind the wheel this weekend. Track was pretty fast and rubbered up. Saw some improvements on the tire performance. Tried increasing pressures a bit, but tires still fell off after lap 6 or 7. Just have to attack corners differently and avoid any sliding.

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To go fast with the Mojos, the kart has to be working correctly and not flat sliding. This is true for all tires but the Mojos seemed to be especially sensitive to this. Work on not sliding the kart on entry and get it to roll. It’s tough to go fast, yet go slow. I also think the current generation of OTKs don’t like to be driven with zest.

The kart should be rolling through the esses at PKRA without sliding.

I’ve almost mastered the esses and hitting the last one just right to setup for the hairpin. It’s definitely a very flowing track and you have to drive that way. Almost have the track figured out and now I find out I have to learn it in reverse… Saturday is CCW and Sunday is CW.

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Does anyone know the recommended cold range for Mojo D5? On the site it just says 8psi.

Is it correct to think you wear out the tire faster at higher pressure? Would you say 100 laps is max for these tires?

Very track dependent on wear. Couple weeks ago I got 60-70 good laps out of a new set. Yesterday hot as hell and abrasive track I managed 40-50 laps. Set them high at like 12 psi turn 4-5 laps get them nice and toasty. Drop to 12ish all around. Turn more laps. Come in drop .5psi increments until handling suffered or you start to hop. That’s your racing pressure.

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I run them between 11-13 cold which I thought was really high compared to what Mojo recommends but it sounds like your in the same range. So really it’s max 2 full race days.

Thank you

I’d say so. Depending on how competitive you want to be. Like most tires they are fastest on their first 1-3 laps. If you can afford it I would always run new tires for a race weekend.

I’m actually hovering around the 10-11 hot. I was saying set them high to get them good and hot. Turn some quick laps then come in. Bleed down to 12psi hot as a starting point. Wait for them to fully cool and you’ll have a baseline cold pressure. Keep dropping pressures until you get a handling issue. Go up .25-.5 psi from there and that’s your racing pressures.

I find for qualifying I only go up .5-1 psi from my racing pressure. These tires don’t need lots of pressure to build heat. I believe these tires have a thin tread compared to MG, Vegas, leconts, etc. it takes no time at all for them to come on.

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Hers is an example of some tire wear I’m seeing. These have a race weekend running clockwise 40laps. Practice day hot as hell 30-40laps counter clockwise.
Fronts have plenty of life left. I’m really killing the inside edge of the rears. Set on the kart is blistered after 40-50 laps (not pictured). There is sings of graining as the tires age, but kart wasn’t sliding alot in the rear.
Anyone have some thoughts on how to utilize more of the tread on the rears? (LR inside wear indicator gone, outter indicator halfgone) Wider hubs to keep the contact patch flatter?
Other soft tires MG yellow, Evinco Reds I’ve normally chewed through the fronts and had nearly perfectly even wear on the rears.

I haven’t driven on Mojos in a long time and I know the compound has changed a lot since I ran Rotax, but I do know they always looked feathered like that, even when my kart was good.

Is there a handling issue you’re trying to correct? I ask because sometimes people get hung up on poor tire wear without consideration for the stop watch. If a tire looks like garbage but the lap time is good, maybe you don’t really need to worry about it.

Fairly normal for all four tires to wear the inside shoulder more. My current MG Reds have no dots left on the inside edge and lots of meat on the outside.

If your main priority is getting the tire last longer, it could be worth flipping the rear tires on the rims between sessions to use each side of the tire more evenly.

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I’d say a bit of handling and the loose nut behind the wheel. I think it’s the way I charge a corner that I always have a bit of mid corner oversteer. Besides driving I’ve been working to take more and more front end out of the kart to tame initial turn in. '21 OTK mostly baseline with 2 dot pills on top for less caster, 1 to 2 clicks of negative camber, optional steering column in upper holes for less ackermann. I like a lazier kart and I’m not exactly light up top 5’8 175-180 lbs so I transfer alot of weight around.

Stopwatch is always king. If my setup is fast and this is just how they wear so be it. It’s just one of those things were I’ve yet to experience such uneven wear not just across the rears but mostly front to rear. It’s like the front are just along for the ride and I’m doing all the work/wear in the rear of the kart.

I can make it through a 10-12 lap prefinal, but I struggle on those last 4-5 laps of a 20 lap final keeping the rears working. Wondering if I can get the rears to work more evenly I won’t be cooking the inside edge and losing performance.

I’ll be turning laps this week and snag a picture of the LR on the kart as it looks terrible on the inner edge. Local track PKRA just seems to chew through tires. I was at Grand Junction a couple weeks ago and did the entire Friday practice 70-80 laps and the tires fared much better.

We are driving d5s on a dd2. For all guys in our championship the tire wear looks the same like yours. After the full sunday the innerside is almost gone and outside has atleast 50%. Only the surface looks different for me. Looks like you dont get enough heat into the tire.

Good to know! I think not enough heat would almost be impossible here in Arizona. It was over 100F and track temps in the 130-140F by 8am :sweat_smile: Swapping tires and rims between sessions the rims were almost too hot to handle.

I also drove tony and the steering was too direct for me. The best solution for me was the alternative column and the upper holes. With the standard one and upper position it was not possible for me, the back was sooo loose that it would be only possible to drive it on new tyres.

Years ago befire the d5 were introduced we used tje yellow mgs. Jeez this was a tire you could literally throw the kart into the corner and it would go like on rails. The mojos were introduced and i spent nearly a year to understand it.

You have to be very precise with it. Throwing the kart with d5s is an absolute nogo

I’m doing the same now. Really have to change the way I drive to get the tires to last and work. If you slide the rears on entry/exit or go in to hard on the brakes and lock them up your lap is done until they cool down.

Just seeing if others feel the same and if anyone has a tips or tricks.

Really considering running a set of MXQs to see if I can better control temp/wear, but that might have to wait since I blew my wheel budget on quite a few sets of MXCs this year.

My racing partner uses Q. We’ve been told that Qs are somewhere between the MXJ and MXC. They can be run instead of the MXJ and the MXC when the track has mediumish grip but when It’s hot and super grippy then everyone is on MXC.

Yes my recollection of Mojos was don’t overdrive them. One locked brake it’ll take 1 lap to have tire come back.