Wider front tires
Discussion
If you do the maths on weight dist, the standard factory width fronts (as a proportion of the rear width) appears correct for the vehicle at stated tyre pressures (when cornering with no breaking). Certainly people seems to think that cornering behaviour is pretty good.
Heavy breaking puts significantly more weight up front (due to weight shift) and I guess wider ones running lower pressures may be better from this context... but you'll potentially mess up the cornering ability. This is true of all cars and is one reason why a low Centre of Mass is important - you get less weight shift.
Also messing with the offset (more tyre inboard) can really screw up the handling geometry unless the rest of the steering / suspension is also modified.
Suggest stay as you are and use sticker tyres if grip is an issue.
Adam
Heavy breaking puts significantly more weight up front (due to weight shift) and I guess wider ones running lower pressures may be better from this context... but you'll potentially mess up the cornering ability. This is true of all cars and is one reason why a low Centre of Mass is important - you get less weight shift.
Also messing with the offset (more tyre inboard) can really screw up the handling geometry unless the rest of the steering / suspension is also modified.
Suggest stay as you are and use sticker tyres if grip is an issue.
Adam
i think it is a preference thing
i think you are probably quite correct in what you say
but i think most people want their ultima to handle the way that suits them
so bigger tyres on the front will make the back more likley to step out and hopefully reduce understeer
while this may not be the fastest sulution it is fun
i think you are probably quite correct in what you say
but i think most people want their ultima to handle the way that suits them
so bigger tyres on the front will make the back more likley to step out and hopefully reduce understeer
while this may not be the fastest sulution it is fun
Working on this at the moment Ken, as I'm also looking at DOT-R's and possibly slicks with new suspension and drysump for the engine.
The cornering of the Ultima is pretty good with the 245's up front, but there is still some understeer mid-corner which isn't so bad for a street car. Some of the guys have addressed this by going with more narrow rear tires instead of wider fronts. Like a 285' rear.
I'll keep you posted Ken on what I work out.
Cheers!
-Mack
The cornering of the Ultima is pretty good with the 245's up front, but there is still some understeer mid-corner which isn't so bad for a street car. Some of the guys have addressed this by going with more narrow rear tires instead of wider fronts. Like a 285' rear.
I'll keep you posted Ken on what I work out.
Cheers!
-Mack
On my car it is only the outer edge of the front tire that hits the light box. This leaves room for a 3 inch wider wheel up front.
I'm going with 2 inches wider and a 295/30/18. There are several vendors for this size and the 335/30/18. In comparison the tire weight is 2# less and the diameter is .5" larger than the 245/35/18. I'll ask Kinesis to weigh the wheel before and after affixing the wider inner rim. They estimate a turnaround time of 2 days and a cost of 1K for the work.
I'll update the thread when finished. Next scheduled track day is in November? I'll try to pick one up prior to that time.
ken
I'm going with 2 inches wider and a 295/30/18. There are several vendors for this size and the 335/30/18. In comparison the tire weight is 2# less and the diameter is .5" larger than the 245/35/18. I'll ask Kinesis to weigh the wheel before and after affixing the wider inner rim. They estimate a turnaround time of 2 days and a cost of 1K for the work.
I'll update the thread when finished. Next scheduled track day is in November? I'll try to pick one up prior to that time.
ken
I'm running full slicks. You can get 16" wheels to fit by modifying the parking brake mount. I run 16x10 fronts and 16x12 rears with 22x10x16 front slicks and 25x13x16 rear Hoosier slicks. Car still has some push. For track only use I think the spring rates need to be about doubled. The rear springs need to be a bit stiffer as a percentage then they are. Probably about 100 lb/in more.
Bill
Bill
I've been running 11inch fronts for about a year and they do make a big difference, I reduced the outer rim by 1/2 inch and increased the inner by 2.1/2 inches to reduce the scrub angle.
The car turns in better and seems to feed back more information IMHO, downside, if it's a problem, you need to restrict the lock otherwise the tyre touches the chassis rail, not a problem for track use because if you need that much opposite you are a passenger anyway!!
Tyres are 285/30/18
Cheers
Ian
>> Edited by B1 ECC on Thursday 18th May 21:32
The car turns in better and seems to feed back more information IMHO, downside, if it's a problem, you need to restrict the lock otherwise the tyre touches the chassis rail, not a problem for track use because if you need that much opposite you are a passenger anyway!!
Tyres are 285/30/18
Cheers
Ian
>> Edited by B1 ECC on Thursday 18th May 21:32
Update:
Wheels are at Kinesis to be widened, expect them back in 7 - 10 days.
I took delivery of some Pirelli P Zero Rossos and they were REALLY wide, too wide for the car. Then figured out that I've got the Asimmetrico Direzionale tires on the rear not Rossos. Ordered the right ones again and when side by side it amazed me how much larger the Rossos were when compared to the correct tire of the same size.
I'll post an update on the wider wheels when able.
On another note: I've finally got some of the crest stickers that I ordered long ago time ago (twenty sets of four). The large crest for the side is 4 inches and smaller ones for the front and rear are two inches. Tyey are printed on vinyl and of medium quality. If you want a set for your Ultima (if more people want them I'll order more but would to send this batch to owners only) please send me a self addressed and stamped envelope. Email me for my address.
Ken
Wheels are at Kinesis to be widened, expect them back in 7 - 10 days.
I took delivery of some Pirelli P Zero Rossos and they were REALLY wide, too wide for the car. Then figured out that I've got the Asimmetrico Direzionale tires on the rear not Rossos. Ordered the right ones again and when side by side it amazed me how much larger the Rossos were when compared to the correct tire of the same size.
I'll post an update on the wider wheels when able.
On another note: I've finally got some of the crest stickers that I ordered long ago time ago (twenty sets of four). The large crest for the side is 4 inches and smaller ones for the front and rear are two inches. Tyey are printed on vinyl and of medium quality. If you want a set for your Ultima (if more people want them I'll order more but would to send this batch to owners only) please send me a self addressed and stamped envelope. Email me for my address.
Ken
295/30/18 PZeros fitted. They are about 1/2 inch greater in diameter and when turned strike the light box and the chassis at the same steering angle. There seems to be little reduction in the amount of steering angle that is available. Track day friday at Carolina Motorsports Park with the Ferrari club. Photos to follow.
ken
ken
Edited by k wright on Thursday 27th July 20:23
B1 ECC said:
I've been running 11inch fronts for about a year and they do make a big difference, I reduced the outer rim by 1/2 inch and increased the inner by 2.1/2 inches to reduce the scrub angle.
The car turns in better and seems to feed back more information IMHO, downside, if it's a problem, you need to restrict the lock otherwise the tyre touches the chassis rail, not a problem for track use because if you need that much opposite you are a passenger anyway!!
Tyres are 285/30/18
Cheers
Ian
>> Edited by B1 ECC on Thursday 18th May 21:32
The car turns in better and seems to feed back more information IMHO, downside, if it's a problem, you need to restrict the lock otherwise the tyre touches the chassis rail, not a problem for track use because if you need that much opposite you are a passenger anyway!!
Tyres are 285/30/18
Cheers
Ian
>> Edited by B1 ECC on Thursday 18th May 21:32
How does that effect the car on the road Ian? I'm thinking tramlining and steering kick back. Neither a major problem on track.
Paul.B
Just back from a track day at Carolina Motorsports Park, and thereafter a drive down a very twisty highway, US421 (1,2 & 3rd gear corners).
It is a huge improvement. The front of the car jumps into corners and thereafter the car is easily throttled around the corner. Good off throttle oversteer.
On public roads where conditions dictate the car be steered with the steering wheel only it is again a massive improvement. I'm no longer buring the rubber off the front of the car in tight corners (anyone remember the thread about the burning rubber smell while driving through corners...that smell is your front tires).
The draw backs:
It is a lot of tire to muscle around on poor road surfaces, there is a slight decrease in turning radius and finaly I had to make some small changes to the car. The return flange for the center section is the contact point for the rear of the tire, it must be trimmed off to allow the rear of the tire to rub the small cover that is in the back of the front wing. Lastly the return for the front wheel arch must be sanded smooth. These are small changes with great returns. Photos soon.
My method for selecting an 11 inch rim and a 295/30/18 tire was as follows:
Closed the front completly and thereafter turned the steering wheel until it stopped, on my car this was when the outside of the front tire hits the light box. Thereafter I measured the amount of space left on the opposite side between the inner aspect of the tire and the center section. I have Kinesis wheels but they were made to match the Ultima wheels perfectly.
ken
It is a huge improvement. The front of the car jumps into corners and thereafter the car is easily throttled around the corner. Good off throttle oversteer.
On public roads where conditions dictate the car be steered with the steering wheel only it is again a massive improvement. I'm no longer buring the rubber off the front of the car in tight corners (anyone remember the thread about the burning rubber smell while driving through corners...that smell is your front tires).
The draw backs:
It is a lot of tire to muscle around on poor road surfaces, there is a slight decrease in turning radius and finaly I had to make some small changes to the car. The return flange for the center section is the contact point for the rear of the tire, it must be trimmed off to allow the rear of the tire to rub the small cover that is in the back of the front wing. Lastly the return for the front wheel arch must be sanded smooth. These are small changes with great returns. Photos soon.
My method for selecting an 11 inch rim and a 295/30/18 tire was as follows:
Closed the front completly and thereafter turned the steering wheel until it stopped, on my car this was when the outside of the front tire hits the light box. Thereafter I measured the amount of space left on the opposite side between the inner aspect of the tire and the center section. I have Kinesis wheels but they were made to match the Ultima wheels perfectly.
ken
Gassing Station | Ultima | Top of Page | What's New | My Stuff