Sharing a Car

[Gidyupp]

HI,
My car is destined to move from street/track use to track only I really want to get a full cage around me. As part of that evolution, I'm considering sharing the car with someone else, I'd like to hear others experience with this and how well it has worked out. For what it's worth, I'm licensed, the other driver would be a student.

A few specific questions:

• I assume the run groups generally can't be chosen such that you would not be running back-to-back at some times, or are there always two groups that are separated?
  Assuming you will end up in some back-to-back run groups, did you find that you lost much track time during a driver change? We are different enough size that there would be some fiddling to be done with the harness,
  
  I have been running summer only street tires but will probably be moving to R-comps. With the tires I have been running, they are usually starting to overheat by the end of a session and I need to come in anyway to cool them off. I Doubt that the tires would support back-to-back sessions. Is this likely to be a problem with R-comps?
  
  Did you find that your tires life ends up being shorter overall with double the usage (i.e. you got less total mileage than if the tires were used for one driver)
  
  What other considerations am I not thinking of?

Thanks for the the thoughts.

[zchris]

Well, any tire over driven can be overheated, especially in a heavy car. If not driven to the limit, no problem. The other thing to consider whenever sharing a car is how good is your friendship. I've seen many friendships turn sour over a damaged car. When I use to share a car doing enduros, I would never drive it on the edge. Not worth losing a friend over. The other side of that was if I wasn't fast, the friendship might have been in just as much trouble

[jeffw]

HI,

• I assume the run groups generally can't be chosen such that you would not be running back-to-back at some times, or are there always two groups that are separated?
  Assuming you will end up in some back-to-back run groups, did you find that you lost much track time during a driver change? We are different enough size that there would be some fiddling to be done with the harness,

Generally the licensed groups have a student group in between them on the first day, so if you are both students or both licensed you'll have at least one group in between.

On the 2nd day, you'd likely be back-to back.

[imgon]

I co drove with licensed/student at one event this summer and it was a bit of a challenge. Ideally you will want to run different tires especially if you are ready for R comps so that means tire swaps between sessions. We lucked out that most of the time we had a session between our run groups but even then it was a rush to get ready. Like Chris said you also need to come to the realization that something is likely to happen to the car when the other guy is driving. I had the advantage of knowing I was just sharing for one event and it was my son so it was more a special occasion than worrying about losing track time or car trouble. I imagine the biggest trick will be to make sure the car is dependable and well sorted so that you don't have to be working on it between sessions. You will need to bring extra fuel! For sure you will want to have a plan/agreement beforehand about help working on the car and who pays for what. Good luck.

[962porsche]

should a properly prepared and set up car last for dual drivers ?
by all means YES !
as you know the car will go thru things faster then with just one driver .
it will be a little more then twice as fast . the reason is cool down time .
can you run a DOT R tire yes you again will find your going to use them up twice as fast or just slightly faster then that . but it comes down to proper car setup you should not be over heating your tires or your brakes for that matter .
with dot R's you will want a tire temp of 180 to 200 degrees F. across the face of the tires .
if your not taking your temps and with two drives it becomes very easy to get the data as you have an extra person to get temps the second you pull in then it's time you start to do so in order to get a proper set up so your not going thru tires and brakes .
I can't stress enough how important it is for set up . if your not one to get into set ups and being anal at car prep then dual driving may not be the best idea .
even the simple things like scuffing in a set of tires becomes important to get more life out of them or you may just start using them up . but this means one of the two drivers will lose some track time as to scuff tires you go out and run 3 to 5 laps then pull in and remove them and they will not get used again for another 48 hours or more . it's kind f a PITA to do but you will get allot more life from them .
they offer new tires heat cycled when you buy them . this is better then buyig ones that are not heat cycled but it in no way is as good as scuffing them your self . this is why you see pro race teams still heat cycling /scuffing tires in .
things like brake pads you may have to change up the compound of pads your using ?
if your just using a street track pad like hawk blues your going to need to up the compound to handle the longer time the car will be on the track . the temps from just running one run session to doing a back to back run sessions should not change but the constant temps of 40 minutes will tend to over use a lower compound pad .

[Gidyupp]

The car is a 2011, well maintained and reliable so far. The suspension setup probably leave something to be desired but I'm working on it. Brakes used to be a problem, now running dedicated track Carbotech pads with cooling ducts, that seems to have solved the issue.
I've progressed up the food chain of street tires to the current Bridgestone RE-11s which are shot. I very well may be (likely am) over driving the tires, but the car is not light either. Usually after about 15 minutes they start getting greasy.
When I replace the tires I want to ditch the pig-heavy OEM 19" wheels and move to a lighter 18". which opens up a lot more tire options.
I have not driven on R-comps yet so have no personal way to judge, but the issue of the student co-driver being on R-comps is a concern if I go that route.
I was also kicking around the idea of getting one more set of 19" street tires to use as wets.
Have not been taking tire temps yet, but I plan to next year. I realized that I have no idea what to adjust without that data.

[962porsche]

yes your right about having no data from temps your just peeing in the wind for trying to do any setups .

get a good tire pyrometer stick the tires in the 3 places across the face . I'm sure you know all this .
even though you said your brakes are doing good you still may have to up the grade of your pads one compound .
we do this with the two IMSA GT3RSR . we run a softer pad compound for sprint events but for endurance events we step up the compound . over a long run it does give a better feel and performance of the brakes with longer life .
I may stay away for a dot R tire at least at 1st . the reason is being a student he or she maybe better off on a good street tire . one reason is the learning curve a sticky tire could mask some bad lines another reason is the chance of flat spotting a more costly tire is higher with dot r's . once flat spotted they will tend to roll to the flat spot and lock their again and again and just keep getting worse.

many people over look tire size as being part of how the suspension works . when you up or down size your wheel and tire package your also going to change the handling of the car .
your rolling radius if keeping it the same by down sizing you rim size you will be adding more side wall of the tire this will give the car more roll and yaw in the corners . to compensate you may need to up the spring rate by 75 to 100 LBS and also change the compression and rebound of the shocks for the heaver spring rates.
if you just drop the tire size and keep the same side wall height you will be changing the gearing .this could be a good thing or bad . many time with higher torque cars it's a bad thing .
I just did a tire size test at Thompson a few weeks ago with a Miata my finding were between two different wheel and tire sizes it was over 2 seconds a lap different between the two sizes tested .

[paultg]

You should research track insurance for the car. Not sure how it works if you own the car but he/she Co drives and has an issue.

Might want to consider an RA1 / NTO1 tire also that can work for both of yiuand not flat spot quickly.

[Gidyupp]

You should research track insurance for the car. Not sure how it works if you own the car but he/she Co drives and has an issue.

I usually get it, one co-driver can be included. The problem is that the coverage is void during the time trials. When the car was new (and still had a loan) I was sitting out the TT runs for that reason.

[PaddyMcP]

My co driver has been bringing me down for 10 years now. Finally we decided to buy another car just like the one we had and he crashed that one too... Go figure.

-Paddy