Hi all,
had a ball at Broadford, great track, challenging turns and scenic surroundings. BUT, in the follow up found significant damage on the outside edge of the front left tyre. This was on two different cars, both FWD (Alfa Mito and Fiat Ritmo), with tyres that were relatively new.
Any other competitors face the same issue?
(http://i976.photobucket.com/albums/ae242/jayarrarr/MITO/BF%20Tyre%20Damage.jpg) (http://s976.photobucket.com/user/jayarrarr/media/MITO/BF%20Tyre%20Damage.jpg.html)
Many thanks.
John.
Lack of negative camber and FWD. Perhaps.
Tyre type and pattern?
Maybe it's the Bradford bats too.
"Bradford" Post title corrected :)
Two different tyre manufacturers Michelin and Continental - I know - maybe that's the problem right there.
Standard camber.
No tyre issues with the Mito at other tracks.
Hello John,
What tyre pressures were you running? May have been a bit low given the outer edge scrubbing?
Corners 1/2 and 10/11 will be tough on the LHF. High wear due to overheating?
John, I too had some pretty bad wear on outside of front tyres with the mito although not as bad as yours. Although I did only half the laps that you and Liam did
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Quote from: Colin Edwards on January 23, 2018, 08:48:52 AM
What tyre pressures were you running? May have been a bit low given the outer edge scrubbing?
Corners 1/2 and 10/11 will be tough on the LHF. High wear due to overheating?
Tyre pressures around 37 PSI (hot) at the front, the same as run at other tracks.
The local tyre bloke reckons damage to the tyre is due overheating, rather than hitting kerbs or fenders rubbing.
When I checked again this morning, there is evidence of the same problem on the right front as well, though to a much lesser degree.
Suspects at the moment are:
- Insufficient camber
- Low tyre pressure
- Tyres not up to temperature before hot laps
- Continuing braking through the entry into the highly loaded corners
Unfortunately the last 2 items are behavioral changes, which are much harder to get right!
Hi John,
Although its not much of a comparison, but my son ran 43 cold / 48 hot in the (non r rated) fronts of my 75 3.0.
More often than not a tyre will run cooler at higher pressures.
innteresting given that the silver 156 was running road tyres which were given an absolute bollocking and I don't think they failed. Same hot conditions, the difference perhaps was the 156 has a lot less power. Disappointing failure though 😐
The Dunlop Direzza Z1s on our 75 proved their worth in difficult conditions.
I can definitely recommend Z1s/Z2s (road legal).
Al
Quote from: dominic.morello on January 23, 2018, 09:21:15 AM
John, I too had some pretty bad wear on outside of front tyres with the mito although not as bad as yours. Although I did only half the laps that you and Liam did
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Thanks Dominic - sorry to hear that you had a similar issue.
I think I was braking harder into the corners, but you were getting better drive out of the corners. Maybe the braking contributed to overheating the tyres.
It's been many years since I've run road tyres on our sud car, but I have a very strong recollection of disintegrating a set of bridgestone road tyres in exactly the same way on a hot day at Winton. They got too hot, melted and blistered at the edges like yours have.
My guess (no really a guess) is that you might have done a little better with higher pressures. Several people have told me that heat build-up in road tyres is majorly affected by sidewall movement - road tyres have thin and compliant sidewalls for comfort. Higher pressures will reduce the amount of sidewall flex, at the cost of overall grip perhaps.
Sheldon and I ran our shiny (not) new 156 Twin Spark on the set of mismatched road tyres it came on, a mix of pirelli, continental, and some chinese brand. We ran them at 42F/40R hot, they howled like crazy but didn't blister.
John, completely agree with Evan's comments. The 'flat' edge on the tyre looks like you have punished them but too much movement.
Ya might need a spare set of more suited track tyres for the Mito. Hope your well.
Paul
Hi John,
Powerflex in Huntingdale do poly bushes for the Mito front lower control arm.
The stiffer polyurethane will reduce the loss of caster and reduce the increase in positive camber during "spirited" driving. End result should be less wear on the outer edges of the tires. The front wheels will effectively remain a bit more upright during cornering. This will put more of the tyre on the road and reduce understeer a bit. Tyre will run a bit cooler as the heat is not as localized. Still will need to run tyres at around 40+ psi cold though. Just a thought!
Also wouldn't hurt to have the front end alignment set up by an Alfa specialist who has a decent in-house alignment rig - and knows how to use it. You may have a tad too much toe.
Hi all,
thanks for taking the time to provide observations and advice. With the next Broadford a few months in the future, I've got some time to make alterations that are must haves.
As the wear on the outside edge is significantly higher than inside edge and centre even for other tracks, I think a little more camber is in order. As are the poly bushes.
Alternate tyres for track days - this is next level commitment beyond arrive and drive, this means carrying 4 tyres to the track - the mito is still a daily driver.
Question : Are howling (road) tyres a good thing? Or something to be concerned about?
It does depend on whether you wish to compete for points in standard class, or are happy to compete in modified class. Some people are aiming to be competitive in class, others don't care and just want to have fun.
Poly bushes are counted as a modification, so would put you in modified class.
There are options in 'ultra-high performance' tyres that may perform much better than what you've got but are still not an 'R' type tyre - so they don't count as a modification under our rules. They'll be better on the race track, but probably won't last quite as long on the road?
If you decide you want a set of dedicated track wheels and tyres - I'd still question whether you need to carry them to the track. You could fit them at your leisure at home before an event, drive to the event, drive home, change them back later. Race tyres wear more quickly than road tyres, but driving up the freeway to Broadford or Winton isn't going to kill them too quickly. I drove our car to the track and back on R tyres for years and never considered it significant wear, especially compared to what you do to them on the race track!
Road tyres howl when they're pushed beyond their limits in my experience, I don't think it's a good thing or a bad thing, it's just a thing.
For reference, here's Sheldon pushing his 156TS: https://www.youtube.com/watch?v=iOWxw5o3XBg
Also I'd agree a little more camber might help with more even wear, although Broadford and Winton are always going to chew the crap out of the front left on a FWD car. My front left tyre doesn't last very long on the Sud, and 3 degrees of camber doesn't fix it. Out of interest what is your camber now?
I agree with Evan re the need to take wheels and tyres to sprint events.
Cooper and I used to run a road set and a track set on the 75, fitting the track set (Direzza Z1) before an event and driving to the track. Now we just leave the Direzzas on the car on the car all the time because they are so much better than your average high performance road tyres IMHO. Every time he drives in the wet I feel good about the fact that he is on a really good tyres that are designed for grip not longevity.
Dunlop do the Direzza, Yokohama do the Advan Neova AD08 and Federal do the 595 RSR – all road legal I think.
A blurb about the Yokos below...
The ADVAN Neova AD08 bridges the gap between street tyres and race tyres. Street tyres work well when cold. Conventional rubber compounds reach their limit during high speed driving as heat softening quickly saps the tyres ability to grip the road. Using street tyres on the track can lead to slower lap times and rapid tread wear.
Cheers,
Al
As others have said, classic overheating and very common on softly sprung FWD cars. Given it's the left tyre I'd hazard a guess that long right hander at the end of the lap is to blame.
You can try track tyres but frankly I wouldn't waste my money if you're sticking to standard suspension. They'll do exactly the same thing, maybe even faster if they're soft.
BTW, fallacy to say road tyres need to be bought up to temp before a run. They're a dish best served cold. They're not slicks.
Quote from: Evan Bottcher on January 24, 2018, 10:35:13 PM
Also I'd agree a little more camber might help with more even wear, although Broadford and Winton are always going to chew the crap out of the front left on a FWD car. My front left tyre doesn't last very long on the Sud, and 3 degrees of camber doesn't fix it. Out of interest what is your camber now?
Hi,
At Broadford had 0.9 degrees negative camber. Unfortunately did not measure the toe prior to the tyres being replaced, and aligned.
Prior to Sandown, have setup the front with 2.7 degrees negative, and 1mm total toe out.
Tyre wear seems to be much more even, and temperatures are within 5 degrees across the tyres - albeit when measured on return to the pits. Looking forward to seeing results at other tracks.
The negative camber does not appear to have impacted braking, maybe the electronic traction nanny is taking care of that :)
For those interested, camber was altered by redrilling the upper stub axle bolt hole through the shock absorber mount. Moving the hole inward by each 0.5mm gets you about 0.5 degrees camber.
Nifty tool find, digital inclinometer $30 to the door from Ebay. Has a magnetic base so you can stick it on the brake rotor for checking camber readily. Stated repeatability of 0.2 degrees, which from experimentation is bang on. Love the digital gadgets available now.
Cheers.
Broadford was built for bikes not cars and as such has some challenges. From memory the Alfa Club run the same direction as the bikes (Which is probably what most CAMS clubs do) but when we used to use it we ran the opposite direction. FPV & HSV used to use it for suspension development and they also ran it in the opposite direction to the bikes.
The standard bike direction has a decreasing radius downhill corner which I suspect may be the culprit of your tyre issue. Downhill gives more weight transfer to the front and the decreasing radius just means you haul harder on the steering wheel.
I'd suggest 37 psi hot is under done. I'd be looking for 40 or maybe a touch more. As a starting point you'd be looking for 4 psi or more differential front to rear. But, look at tyre temperatures and use pressure to try and make them more even. If you trim tyre pressure by tyre temperature, you may have similar pressures all round hot, but cold the pressure may be different for each of the 4 tyres.
You need the car to turn in better. Some toe-out at the rear may help this, maybe more at the rear than front. Anything you can do to help weight balance will help - boot absolutely empty, low fuel, etc. Beyond this its trying different lines. A slower entry and later apex may be faster and gentler on the car.