[DaveC113]

Originally Posted by Msquared

Yep, that rake situation is mostly a function of roll center heights (to use old-n-busted terminology). If you lower the front ride height you lower the front RC, which effectively decreases roll stiffness even though the spring/swaybar/damping rates all stay the same. Raising the rear raises its RC, making it more stiff in roll and also adding to jacking during cornering. Either one will shift your cornering balance away from understeer and more toward oversteer. Just know that raising the rear ride height also raises the static CG and the cornering CG, so it's likely to decrease rear grip rather than just increase front grip. So don't make big changes.

Thanks for the input, that makes sense. The GT4R has less rake than stock, but maybe a bit more than my car at this point. Maybe I'll just go for 1/4" and see. If it doesn't change alignment a lot I might have to try a few rake settings at a test n tune.

[Msquared]

Originally Posted by DaveC113

The GT4R has less rake than stock, but maybe a bit more than my car at this point.

That is relevant if - and only if - the GT4 has the same suspension pickup points as stock. Also, I'm assuming that car has adjustable spring perches at least at one end? If so, whatever's shown in that pic can be adjusted. Regardless, it's a tool you have available, so it's worth experimenting in small adjustments. You don't want to go too high because jacking and higher CG are bad. You don't want to go too low because you'll get more roll and start hitting bump stops, but 1/4" either way is not unreasonable at each end to experiment with.

[DaveC113]

Originally Posted by Msquared

That is relevant if - and only if - the GT4 has the same suspension pickup points as stock. Also, I'm assuming that car has adjustable spring perches at least at one end? If so, whatever's shown in that pic can be adjusted. Regardless, it's a tool you have available, so it's worth experimenting in small adjustments. You don't want to go too high because jacking and higher CG are bad. You don't want to go too low because you'll get more roll and start hitting bump stops, but 1/4" either way is not unreasonable at each end to experiment with.

Thanks, I believe it has the same sus and ft/rear are fully adjustable. In some setup notes I found for driving the GT4R on sim, they mention rake as promoting rotation, but for autox we get more rotation because we're in 2nd gear, which rotates the car a good bit more than 3rd and 4th.

Judging from my results last season I probably don't want to make large changes, I had a few very experience codrivers and a track instructor who were very happy with the car's setup. One of my codrivers is now about to purchase a SS 1LE after driving my car, he's been autox'ing for 20 years and has some very impressive times at local tracks.

If you browse pics of GT4Rs online it doesn't seem like they vary rake all that much, in general I think it's less than a stock SLE or ZLE and a bit more than my car currently runs.

[DaveC113]

Getting there!

So far I replaced the front tension/radius arms as the bushings were toast, just got some ZLE arms. I looked at SPL and I think they're inferior to OEM while costing a lot more.

I did an alignment and created more space in between the tire and spring perches. I spend a little bit of cash on a home alignment setup and it's awesome. Took a few minutes to get setup right but once you get the hang of it it's pretty simple.

I installed Race Louvers fender vents. This was a larger PITA that I thought. Supposed to be for the Camaro but it's flat and the fender is not. Race Louvers seems like a decent product, but pricey for what it is. I cut some holes in the fender liners and covered the holes with screen material.

I installed flares on the front fenders, it turned out decent. I'm going to make a flat flare that attaches to the same points as the flare so I can run narrower wheel/tire setups without it looking ridiculous.

The rear barely fits. I need to adjust the point where the rear bumper cover meets the steel fender, there's a sharp fold there that is the only thing that could be a real issue. It looks like the tire is touching the fender in the pics, it is but just barely... so barely there's no friction. I think I can get away with running the rear fenders as-is and just adjusting that one little sharp part.

[apexit53]

thats some classic bmw tuck right there!!! lol nice.

[DaveC113]

I finally got the car ready... changed fluids, installed new front rotor rings, vinyled the flares and put the 345 P1s on, wheels are Apex 18x12 et41. Fronts use MSI Mustang wheel studs and 38mm spacers. The car is a little lower than stock, I honestly have no idea how much, lol.

Eventually I plan on having 3 sets of flares, a flat flare for OEM 10" wheels, and a flare that's otherwise the same as the pic but sticks out about 1" less, those would work well for 11" wide wheels or running a stretched 12" fitment.

Car drives well, steering feels responsive and accurate so far, a bit softer than the REs, but I was running 295/35 on the same 12" rims, which was pretty stretched but worked really well, I might get another set as I got a smoking deal on another set of 18x12s I couldn't refuse. I theorize the REs will be better for events where the tires won't be as hot, or if it's moist REs are clearly superior according to GRM tests. It would also be interesting to see if I can compare them at HPR or an autox. I couldn't corner anywhere near the limit but I can say the P1s put power down pretty well.

[VR Baron]

Originally Posted by DaveC113

I finally got the car ready... changed fluids, installed new front rotor rings, vinyled the flares and put the 345 P1s on, wheels are Apex 18x12 et41. Fronts use MSI Mustang wheel studs and 38mm spacers. The car is a little lower than stock, I honestly have no idea how much, lol.

Eventually I plan on having 3 sets of flares, a flat flare for OEM 10" wheels, and a flare that's otherwise the same as the pic but sticks out about 1" less, those would work well for 11" wide wheels or running a stretched 12" fitment.

Car drives well, steering feels responsive and accurate so far, a bit softer than the REs, but I was running 295/35 on the same 12" rims, which was pretty stretched but worked really well, I might get another set as I got a smoking deal on another set of 18x12s I couldn't refuse. I theorize the REs will be better for events where the tires won't be as hot, or if it's moist REs are clearly superior according to GRM tests. It would also be interesting to see if I can compare them at HPR or an autox. I couldn't corner anywhere near the limit but I can say the P1s put power down pretty well.

Wow, really nice job!

[apexit53]

looks awesome!

[DaveC113]

They seem to work! I managed FTD at a local BMW autox, there are 20 or so good drivers and usually a handful of top level drivers. I got beat by one, but am super happy to get within a tenth of the winner. IMO, the PAX differential is a little too small, but I'll take it, lol. Nice to see a Camaro 1-2 as well.

The tires started out pretty bad but it was cool out in the morning and the tires only has about 60 street miles on them. They were heat cycled by Phil's. In the afternoon we got 4 more runs, it was in the low 70s and full sun, so the asphalt surface was warming up. Times went way down all around and the P1s were somehow even worse on the 1st run in the afternoon, but the 2nd run was 2s better but still weren't right, 3rd run was FTD and 4th run I overdrove intentionally to see what happens. Well, the tires are really good at and beyond the limit. They tolerate a larger slip angle without losing grip so you can drive on the edge without a small error being as catastrophic. This may be the big 345 advantage, but power down is excellent and braking is ridiculous, will say more on that later. Downside is they need too much heat for some situations and aren't great in the wet, so it's hard to see these as the only set of ax tires if you're serious and travelling long distances to compete, you need to have a set of competitive tires and P1s may not be it, but keep reading as these are amazing track tires too. So I'm using the P1s for hot weather/codriver, etc. autox and track, and then a set of REs in 295/35/18 for cooler days or SCCA events with longer intervals and fewer runs, BMW usually gets about 80 attendees, SCCA can hit 140.

I went to a track day with PCA today, I just started with them and don't have a ton of track driving experience, so I'm driving with an instructor in intermediate group, which has both solo drivers and drivers with instructors. Luckily my instructor wasn't fat, lol. I was the fastest of 30+ cars but tbh the only other competent drivers were in two GT4s, both running REs and at some fairly high level of track prep including roll bars, seats and harnesses. One was driven by an instructor with experience driving race cars, so I feel super happy the SLE could pull that off, despite the fact I'm not as good of a driver as the two GT4 drivers. There were some GT3s that would have smoked all of us but most intermediate drivers aren't fast. It's a big jump to the fast group though. There are a lot of amazing P-cars at these events that are way faster than a SLE.

Previously, I used the OEM GY SC3s on track, which are great tires but nowhere near the grip of the P1s, I mean not even in the same realm. I run Ferodo DS3.12 track pads and could invoke abs pretty easily with the SC3s, I never even got there today with the P1s, and I was gaining 2 car lengths on the GT4s in the braking zone. The braking grip is just on another level, and it's already way better than average with the SC3s. Cornering is significantly better too, about .1-.15 or so more average gs just estimating from the dash readout. It was also low 70's today, the P1s came on within a lap (2m), and didn't seem to overheat in a 20-25min session.

Wear looks decent, will have to take some pics later.

Overall, I like them a lot. For autox, if you have the use case I think they are faster than the others but I'm not sure how much is the size and it's hard to quantify differences. I may get a chance to test the 345 P1s vs 295 REs though, overall as I said I think P1s are probably faster but given both are performing ideally I don't think your choice of 200tw tire is a big deal. While P1 may be faster I think we're talking a couple tenths or so, but I could be wrong, my seat of the pants opinion is not a timer, and timers are what matters so this would require testing to draw any real conclusions, and also the differences are small enough other factors may be too difficult to completely control for results to be significant.

For track these seem like they are up there with real R-comps like GY SC3R and Cup 2 R. Again, would require testing. If so, they probably last longer, those are 100 tw I think. I was really impressed with these on track from the perspective of a more casual HPDE use, but some P-car owners were a little shocked at how quick the Camaro was.

[DaveC113]

I ended up getting a set of RE71RS in 295/35/18 as well. I ran them last weekend and my overall result was similar despite the REs being less than optimal when brand new. I did get the Tire Rack heat treatment which helps a lot. It makes them much faster at the first event and more consistent during their lifetime.

I would speculate the P1s are faster if you can get them up to temps and so far I think the power down and braking are likely their largest advantage. An extra 50mm of tire probably helps there, lol. There's probably less difference in cornering grip.

Anyhow, here's results from SCCA event #2 at CO Air and Space Port. I was P2 until the last run of the last heat by a new driver in an '18 GS Civic Si sent me back to P3. Nobody was all that close to the winner, but even so I'm super happy to win over Darden, who beat me last weekend by less than .1s.

So far I'd choose the REs as my only set of autox tires as the P1s take too much heat for some events. However, I am extremely happy with the P1s on track and there's no way I'd go back to SC3s. It'll also be great to have the option to use P1s on hot days or if I have a codriver, so I think they will get plenty of autox use. I can see needing a 2nd set this season as I'm trying to get more track days in.

[apexit53]

is there a way you can test them on the same day back to back?

The cam challenge in st louis the vitour was less than optimal for a lot of drivers. they need some heat and we did not have that this weekend.

The falkens however were amazing. Needed one good lapt to get them up to temp, stayed consistent. in the challenge i ended up spaying them just to try and keep them consistent since the challenge we were kinda hot lapping.

[DaveC113]

Originally Posted by apexit53

is there a way you can test them on the same day back to back?

The cam challenge in st louis the vitour was less than optimal for a lot of drivers. they need some heat and we did not have that this weekend.

The falkens however were amazing. Needed one good lapt to get them up to temp, stayed consistent. in the challenge i ended up spaying them just to try and keep them consistent since the challenge we were kinda hot lapping.

Back to back is going to be tough as there aren't a lot of test n tunes on the schedule. Both BMW and PCA do morning/afternoon runs, but that's not going to be valid as here in CO there's often large temp differences and hence large time differences between sessions. I think the differences between the tires aren't going to be apparent in any one test either as conditions may be more favorable to one tire, I think results will depend on the surface and/or temps at the time.

If both tires are at their optimal, I'd guess that P1s are going to be faster. I think REs will likely provide more consistent results, but on a hot day you may get fewer runs at before the REs fall off. After driving the P1s on track I doubt they will ever fall off due to overheating at an autox.

There's some car dependency too, some fwd'ers are trying P1s up front and A052s out back. My friend Van's GS Acura puts a lot of heat into the front tires as the car is heavy and the tires are relatively small, so I can see P1s being really good there.

I've always liked the Falkens but they fall off too quickly, after 5 or 6 events or 30-40 runs they slowly fall off. If the new "+" version does not I think they'll be a good option. REs don't last that long either but seem to maintain their grip consistently throughout their life, then fall off a cliff.