I just pulled the trigger on the V710s and was wondering if I could get some suggestions on the pressures. I know there are a bunch of topics on pressure settings for the V710s, lots of 34-37psi suggestions along with Per's 44-47psi numbers published in GRM.

While that is good info, I am not sure it translates directly to my application for the following reasons:

1. I will be running 205/50/15s on 15x7 wide wheels rather than squeezing the wide tires on a narrow wheels as people have to do for stock classes. I would think that the wide wheel should enable me to run lower pressures. Kumho also recommends running as low as possible for better grip and tire wear... but how low should I go?

2. I have camber plates and currently run 2.2 degrees ~ 1.5 above what the stock cars get. I am guessing this will also enable lower pressures as rollover is reduced via camber.

My car is a no options 04 MC with SS+ ...

Oh a side note, the V710 literature claims that the tire is designed for cars running 0.5 to 1.5 deg of negative camber - should I be considering dropping my camber from 2.2 to around 1.5?

 

I have run a 2003 MCS with front camber at -2.3 degrees, coilovers, and 15x7 rims with V710s at autocross for two seasons in the past.

You can run lower pressures down to about 35 psi front and 32 psi in the rears. You can go up or down from there by about 3 psi.

There are many variables so try things out and measure tire temperatures after about 3 runs using a probe type tire pyrometer. See how even the temps are in the front or back tire across right middle and left on the treads.
If you run hot then wet down the tires in between runs with water spray, it can be helpful.

Keep your front neg camber it's fine. What are your other alignment settings?
Front toe, rear toe, rear camber?

What class are you in? FSP sounds like?

 

I guess the mods (cambe and R-comps) would put me in FSP at SCCA events but I usually run with BMWCCA so I get to fight it out with a bunch of M cars on street tires. Power vs superior transitional handling i guess.

My alignment specs:
front camber -2.2-ish
front toe 1/16" out (although the right front wheel is more like 3/8" because the tie rods froze)
rear camber -1.3
rear toe 0

I got freaked out a bit after I read Kumho's literature saying the tires are designed for up to 1.5 degrees of neg camber. They claim anything above that might not utilize the outside round edge of the tire, which will result in slower times. Sounds fishy, but you'd think the manufacturer knows their product best...

Definitely need to get my hands on a pyrometer - on my christmas wish list for next year.

Since I have your attention minihune can you quickly answer two questions for me?

1. Winter storage for brand new V710s - plan was to bag them, use a shop vac to suck most of the air out, and put them in a cool basement in a corner away from most electronics. Anything else I should do?

2. Breakin/heat cycle - i was planning on driving 10 miles at 50-60 mph to an empty parking lot, tossting the car around for a minute, swapping the tires front and back, tossing the car some more, driving home. put them aside in the basement for 48 hours. am i missing something?

Thanks!

 

I am watching this thread as 710s are on my list for next seasion.

Great questions

Awesome information !

 

Your alignment is OK. Stock rear sway bar? If they allow it in your class, you might consider an adjustable three hole 19mm rear bar.

You can borrow a pyrometer if you know someone that has one. You only use it a little to get a handle on how much pressure to use and how your alignment is working for you.

There are two kinds of pyrometer one is probe style and one is infrared. I like the probe style for accuracy and you can use it on tires or on a hard surface like for brakes. I bought mine on Ebay.com.

For storage- don't put any tire treatment on the rubber sidewalls. Put in about 36 psi to store and check the pressures every two months. Don't put anything heavy on the tires. Realize that time will harden the rubber so any tires that are sitting and getting old are not going to be a sticky and soft as new rubber bought in the spring. Therefore it makes more sense to buy tires that will wear out at the right time before winter then buy new tires in the spring so you don't have to store and use older tires.

For heat cycling I like tirerack.com's service to heat cycle without wearing tread. It's done consistently for each tire and better than you can do yourself. I've tried to heat cycle but it's not as easy as it might seem. I tried driving in a circle and on the highway but the temps hardly increased and I didn't want to drive too far and wear the tread.

If you already have the V710s then you just have to find a remote site and go around in a large circle to generate some heat but without a pyrometer you won't know how hot you are getting. Figure you need a temp of about 130-145 degrees although track operating temps are about 160+.

Tossing the car around for a minute might not be enough. At autocross I drive about 30 turns in 30 seconds and there is barely much rise in temps about 120 degrees. Another run out and it gets hotter. Third run better about 135 to 140 degrees.

Driving 10 miles to the site is hazzardous for your V710s. In transit one of the autocross drivers was on the highway using Hoosiers and ran over a bump in the sectional expansion joints which caused his MINI to hit the wheel arch on this tire and it cut the tire tread. What if you pick up a nail? Too risky for new tires.

If you do order heat cycled then you scrub in the outer surface of the tires but driving a little in the parking lot to remove the top layer of rubber. I always order heat cycled.

One other tip is you don't have to balance autocross tires- leave the weights off, saves weight a little and the expense. You're not using them for long distance driving. Weights can be used for track wheels where you are doing lapping.

 

minihune, i know what you mean about buying tires early. I saw the V710s on special at the tire rack, my current r-comps are just about dead, so I figured I would pick the V710s up for spring. The $122 price (instead of the $180+ during high season) was hard to pass up. If properly stored, do you think the rubber properties will change so much that they will become noticeably slower? (noceably being more than a tenth or two on a 45 second course).

Regarding storing them. They are brand spanking new. My plan was to not mount them, not scrub them in, keep the mold release or whatever on and just bag them, get as much air out of the bag as I can and keep them in a dark basement. Are you suggesting that I mount them on the wheels and get them up to 37psi before storing them? If so, do you think they should be initial heat cycled before storage or after?

EDIT: Looked around and Toyo seems to recommend storing their RA-1s completely deflated.

 

OK, that's different if it is not mounted.

Yes, what you proposed is OK. I'd check with Alex@tirerack.com as well on the storage.

Leave it unmounted and store without using, keep out of sunlight and heat.

Once you start using it and do the first heat cycle then it starts aging. The more you use it the faster it ages. Unused is good to store.

 

I checked with Alex and he said the storage approach makes sense - dark basement, black bags sealed to keep air and light out, unmounted/unused, keep off the cold concrete. For initial heat cycle he recommended driving up to 30 minutes at highway speeds.

Thanks for all the help mihinune!

 

OK, I agree with the plan your have which is sound.

Only other thing is age- tires cannot last forever so keep track of how they do when you get them mounted and see how long they last when you buy early and store.

30 min x highway speed is- 0.5 hour x60 mph = 30 miles of tread lost and risk of harm to the tires from road hazzards- do it when visibility is good and traffic is down, not on a stretch driven a lot by trucks. As the tires heat up and the tread gets soft they tend to pick up all sorts of road debris and trash. Things don't bounce off, they stick which can include glass and sharp metal.

I'm usually very strict about my tires. I do four runs of 30 seconds each event and hope to save my tires for 10-12 events per year/season. I heat cycle with tirerack to save wear on my tires plus they do a better job than I have been able to do- I've heat cycled two sets of R compounds on my own and the wear on the tires over a season each time was not to my liking. Not sure if the heat cycling I did was enough.

4 runs x 0.5 min x 12 events/year = 24 minutes or 24 miles of use each season to keep the tires as close to prime operating condition. Others are not strict and will drive their tires on the freeway to get to events some 8-10 miles each way.

 

I'll probably go out early morning on a weekend and drive up the turnpike, hopefully the lanes will be clean. Losing some tread due to heat cycling is definitely a bummer but since I will just be driving in a straight line, I hope it won't be too much wear.

You seem to think that the V710s don't stay at peak for very long. Most of the reading I did suggested that they stay pretty consistent for the first 60 or so 45 second runs and then fall off (by about .5 to 1 seconds) for the next 60 runs before they finally cord.

I was hoping to duplicate that kind of longevity with this set.

 

Depends what you define as peak.

0.5 seconds is the difference between 2nd and 10th place overall in my area. I usually have to fight for every 0.1 seconds I can get and in the past even in my class I have won or lost by 0.01 or even 0.002 seconds.

If I have tires that give up that much it's time for a change.

For my bad handicap in SM class I need to be top 3 to make any impact on overall times with PAX applied. Top 10 is not enough and 1/2 second too slow for what I want to do.
Tire preservation is key. Probably what hurts my tire performance the most is time- being used for the whole season. Tread is fine but rubber gets hard with time and UV light exposure since I am out there all day long usually 10 hours each event.

 

I have been running 45# front and 50# rear but after reading Kumhos literature I see they are recommending tire pressures in the thirties and low forties. Anyone out there running a Kumho 215/40x16 and if so what pressures do you run?

I read somewhere that Per (GRM) had stated 45# front and 55# rear. I have been jumping all over with pressures and should buy a pyrometer. Any help will be appreiciated.

Thanks Terry

 

Every track surface is different- the more rough it is (like concrete) the more grip you have with your tires and the faster they warm up.

The longer the course and the more turns the more you warm up your tires.

The smoother you are in transitions from right to left or coming out of a sharp corner the less you heat up your tires.

The longer the waits between runs and the more you cool them off with water the lower the temperatures and pressures.

Using chalk to mark the edges and a pyrometer right after the 2nd or 3rd run helps you see where the best pressures are given your driving style and your track surface.

What works for one person doesn't always work for others even in the same event. Sometimes we run a little higher or lower because it feels better.

Lower pressures tend to use more of the tire with some rollover on hard turns. It usually doesn't feel as nimble as higher pressures.

You are in what class? Per is in G stock with limited camber. I'm in Street Mod with -2.5 degrees front camber and -1.3 in the rear. I run higher temps in front and lower in the rear by 3 psi. I've run V710s as low as 33 front and 29 rear with some success, and now I run Hoosier A6 with 41 front and 37 rear.

 

I have been running in the DSP with my 06 MCS JCW. Front camber is 2.3 with 1/8 toe out. Rear is 1.3 and 0 toe. I use an H sports rear bar ( center hole)and a stock front. I hope this helps.

Thanks for your response....

Terry

 

Per is running MCS in G-stock and doesn't have your front negative camber advantage.

I'd suggest running higher pressures up front and chalk your tires front and rear and check tire temperatures using a probe style pyrometer.

You didn't mention your exact suspension specs (JCW?) but you can try
Front 45 and rear 40 psi and see how it goes both with your judgement of how it feels and how the tire temps are looking. I would think front vs rear pressures would be about 3 to 4 psi difference. Lowest I'd suggest is about front 36 psi and rears 33 psi but that would vary with the course layout/surface. Handling won't feel as crisp and you'll get more rollover but you'd use more of your tires.

 

Thanks Minihune, I tried running more pressure in the front the opposite of what I have been using and the car was quite good. After two runs the old way I switched the pressures around and not having a clue of how it was going to handle I went slightly faster. On my fourth and final run I was going to push it a little harder. Green flag drops and I miss second gear so I continue on until I get to the salom which has decreasing distance between cones I can bearly make the last cone which almost causes a stop and turn. Not pretty. The rest of the run was fine and my time was almost one second faster than previous. I cannot wait to the next event as I feel the handling is now controlled and in the sweeper I can go from oversteer to drift to understeer using throttle. Your comments on Par's car made sense as he is limited to stock camber.

thanks again Terry
PS took a third place at that event

 

Reviving the thread. Autox season is close and I am planning on doing a home brew heat cycle on the V710s as soon as a semi warm and dry weekend comes our way.

I have a probe type pyro so I can actually verify that the tires are up to proper temperature. I just don't know what that proper heat cycle temperature is.

Kumho says the optimal operating temperatures are 180-220 degrees F. What should the heat cycle target be? Should I be aiming to get the rubber up to 200 degree sweet spot? My thinking is that my target temperatures should be lower, cause I don't want to overheat the tires on the first go. So, what should I aim for? ~150F for the initial heat cycle?

thx.

 

I have owned and used sets of Kumho V710s three times and only on the track do I get temperatures at 180 or higher.

For autocross use I barely can get to about 120-130 degrees. Most of the time it's lower. I think that if you can get to about 130-140 degrees that's good enough for heat cycling new tires.

Typically you need to be driving in a large circle as fast as possible to get the outer tires heated up then circle in the opposite direction to heat up the other side. Make sure tire pressures are not too high or you'll overheat the center tread.

I usually try to do some driving on the highway and take some on and off ramps fast but I worry about wearing out the tires at the same time.

You can always buy the tires heat cycled by tire rack to avoid problems. If you roads are cold due to the weather that would make it harder to heat cycle.

 

Interesting about the temperatures. I remember seeing (and reading about) folks using a water sprayer to keep V710s cool on a hot autox day. Has the rubber compound or construction changed in the last couple of years? Or is overheating only a problem on very hot days?

 

Depends on the cars. In my area there are Miatas that do very well and heat up the tires much more. They use water spray between runs to cool down the tires. I have the opposite problem yet our run times can overlap.

Your suspension, wheel width, alignment and driving style are factors in how much you heat up your tires.

The smoother you drive the less you overtax your tires and use them to their fullest capabilities without having to generate excess heat.

 

This is a bit of a tangent, but I as just packing the V710s up to take them to a tire shop tomorrow for mounting and balancing and I noticed that the date tag following the serial number said "2005" on one tire and "2505" on the other.

If I understand tire date tags correctly, that means these tires were made in mid 2005 and are therefore 3 years old. I bought them from the Tire Rack in September of 2007 and nobody indicated to me that they were 2+ years old.

Is this a problem? Am I going to get noticeably degraded performance? Should I be calling TTR and asking them what gives?

 

What size are the tires?

I got some about December that were also dated in 2005 and were on sale for $122 each for 205/50-15. Older production, so lower priced compared to the more recent ones I purchased this week made in the 32nd week of 2007 and were 225/50-15 for $184 each.

Yes, the more recently made tires are better and fresher. I'm not sure if you would be able to tell the difference when new or if it affects much of the life span of the tire based just on age vs the way you drive on them, store them and maintain them once you get them.

By comparison I also bought Bridgestone street tires at the same time as my newest V710s and they were made in the 37th week of 2007.

 

I got the same exact tires you did. Bought them in Sept of last year, 205/50/15 at a great price of $122 each. So we must have gotten tires from the same "batch".

I guess I won't worry about it. These are my first top tier autox tires - I have plenty to learn on them and they will be way faster than my badly abused and scalloped RA-1s.

 

Somehow I knew Minihune would be in on the V710 conversation. I FINALLY picked some up for my R50 (used from MakakiloMini) FINALLY getting to Autocross. Yay!

 

In theory, one should run a little higher pressures with a wider wheel than with
a narrower wheel - especially regarding keeping tire wear even across the tread.