Need someone good at maths help

[kinkyllama]

I know I've made a post on this before but maybe this will get more attention. I really need help figuring out what offset I need for my wheels to fit... I dont wanna spend over 1k for wheels that dont fit as well as they should.

I found a wheel offset calculated...and according to it to get a wheel that has the same inner clearance as my current track wheels I'd need a +15 offset for 9" wide wheels. I need to know how much less clearance I'll have at the top of the tire with -3 degrees of camber compared to what I have currently (-.3). If I could get -3 degrees of camber now I would so I could test fit, but it wont be several months before I can reach the camber I need (I'm already maxed out) and I need to buy new wheels within two weeks to fit my wide body.


http://www.1010tires.com/WheelOffsetCalculator.asp

According to it I have 11mm more clearance with my 17x7.5" +45 wheel than I do with my 16x7 +40 wheels. One problem is I have to have a 5mm spacer (making my 16x7" wheels +35) to fit my 16" wheels over my brakes. I want my new wheels to be as close to the middle of the car as possibe with -3 of camber in the front without rubbing. How many mm are even in an inch?

Help!,
Danny

[PrecisionBoost]

25.4mm in an inch.

That's quite a question..... clearance partly depends on the inner fender.... with a change in camber it might change which part of the tire comes closest to the inner fender... since the fender is not an even shape.

Plus your car is lowered.... so that will make a difference

I looked at my setup at one point and felt I could move the back of the tire in towards the center of the car ( called backspacing ) another 1/2" (12mm)

The camber adjustment will defnitly push the inner edge towards the center of the car.

Well.... I'm going to take a stab at this... but I can't guarantee I"m right about it.

Basicly.... we need to figure out the radius of the tire.... since the diameter of the stock ones are

If your running a 205 45-16 tire the diameter would be about 23.1" which makes the radius 11.55"

To calculate the amount the tire will be pushed inwards we use the "tan" function

Tan (angle) = OPPOSITE / ADJACENT

TAN ( 3 degrees) = OPPOSITE / 11.55"

OPPOSITE = 0.605"

So based upon my calculations changing the camber by 3 degrees will push your tire inwards 0.605" which happens to be 15.4mm

I know this is only part of the equation.... but it should help straighten out what will happen with the camber.

If it were me........ I would jack up the car on the driver side so that the driver side wheel is 8" off the ground.

This should put quite a bit of weight onto your passenger side and force the shock to compress.

I suppose you could also lift the passenger side up 8" and put something solid under the tire.... such as concrete blocks (make sure they are in good condition)

Then you can get in there and measure the clearance to the inner fender.

I would do it three times..... once with the wheel straight.... once with the wheels turned as far left as possible.... and once with the wheels turned as far right as possible.

Ideally.... you might not want to turn the wheel while it's up in the air.... it might cause the blocks to slip out.

If you can.... see how far your shocks have before they hit the bump stops..... this will let you know if your close to the maximum suspension travel.

Ok.... once you have the tires in these three positions.... I would measure the clearance on all areas of the tire and write them down.

These measurements will allow you to get a good idea of how wide the tire can be.... and where it must be positioned relative to the center of the suspension/brake mounting point.

If you got these dimensions I could help you figure out the exact offset and width you can go with.

Hmmmm..... your doing a "wide body" kit right???

I'm assuming your going to cut out part of the inner and outer stock fenders so that you get more wheel clearance.... am I right????

[kinkyllama]

25.4mm in an inch.

That's quite a question..... clearance partly depends on the inner fender.... with a change in camber it might change which part of the tire comes closest to the inner fender... since the fender is not an even shape.

Plus your car is lowered.... so that will make a difference

I looked at my setup at one point and felt I could move the back of the tire in towards the center of the car ( called backspacing ) another 1/2" (12mm)

The camber adjustment will defnitly push the inner edge towards the center of the car.

Well.... I'm going to take a stab at this... but I can't guarantee I"m right about it.

Basicly.... we need to figure out the radius of the tire.... since the diameter of the stock ones are

If your running a 205 45-16 tire the diameter would be about 23.1" which makes the radius 11.55"

To calculate the amount the tire will be pushed inwards we use the "tan" function

Tan (angle) = OPPOSITE / ADJACENT

TAN ( 3 degrees) = OPPOSITE / 11.55"

OPPOSITE = 0.605"

So based upon my calculations changing the camber by 3 degrees will push your tire inwards 0.605" which happens to be 15.4mm

I know this is only part of the equation.... but it should help straighten out what will happen with the camber.

If it were me........ I would jack up the car on the driver side so that the driver side wheel is 8" off the ground.

This should put quite a bit of weight onto your passenger side and force the shock to compress.

I suppose you could also lift the passenger side up 8" and put something solid under the tire.... such as concrete blocks (make sure they are in good condition)

Then you can get in there and measure the clearance to the inner fender.

I would do it three times..... once with the wheel straight.... once with the wheels turned as far left as possible.... and once with the wheels turned as far right as possible.

Ideally.... you might not want to turn the wheel while it's up in the air.... it might cause the blocks to slip out.

If you can.... see how far your shocks have before they hit the bump stops..... this will let you know if your close to the maximum suspension travel.

Ok.... once you have the tires in these three positions.... I would measure the clearance on all areas of the tire and write them down.

These measurements will allow you to get a good idea of how wide the tire can be.... and where it must be positioned relative to the center of the suspension/brake mounting point.

If you got these dimensions I could help you figure out the exact offset and width you can go with.

Hmmmm..... your doing a "wide body" kit right???

I'm assuming your going to cut out part of the inner and outer stock fenders so that you get more wheel clearance.... am I right????

Wow I can't beleive camber will push the wheel that much closer.

I'll do this as soon as I get time (probably Monday).

What do the bump stops look like anyways? I'm pretty sure I dont have even a 1/2" before I hit them as even on full soft with as low as my car is the suspension feels like its traveling only 1/16th of an inch. Also I'll probably be raising the car slightly with the new tires. The biggest tire I have on the car now with this ride heith is a 215/45/16" and I will have a 255/40/17 for the track...untill recently I always though the sidewall measurment was mm or something not a % of the width so my new tires are gonna be much wider which means I'll have to raise the car a bit.


I do have two 255/40/17 tires mounted on my 17x7.5" +45 wheels. I'll put those on for the measurments.

Thanks so much Chris! its a huge help!
Danny

[kinkyllama]

25.4mm in an inch.

That's quite a question..... clearance partly depends on the inner fender.... with a change in camber it might change which part of the tire comes closest to the inner fender... since the fender is not an even shape.

Plus your car is lowered.... so that will make a difference

I looked at my setup at one point and felt I could move the back of the tire in towards the center of the car ( called backspacing ) another 1/2" (12mm)

The camber adjustment will defnitly push the inner edge towards the center of the car.

Well.... I'm going to take a stab at this... but I can't guarantee I"m right about it.

Basicly.... we need to figure out the radius of the tire.... since the diameter of the stock ones are

If your running a 205 45-16 tire the diameter would be about 23.1" which makes the radius 11.55"

To calculate the amount the tire will be pushed inwards we use the "tan" function

Tan (angle) = OPPOSITE / ADJACENT

TAN ( 3 degrees) = OPPOSITE / 11.55"

OPPOSITE = 0.605"

So based upon my calculations changing the camber by 3 degrees will push your tire inwards 0.605" which happens to be 15.4mm

I know this is only part of the equation.... but it should help straighten out what will happen with the camber.

If it were me........ I would jack up the car on the driver side so that the driver side wheel is 8" off the ground.

This should put quite a bit of weight onto your passenger side and force the shock to compress.

I suppose you could also lift the passenger side up 8" and put something solid under the tire.... such as concrete blocks (make sure they are in good condition)

Then you can get in there and measure the clearance to the inner fender.

I would do it three times..... once with the wheel straight.... once with the wheels turned as far left as possible.... and once with the wheels turned as far right as possible.

Ideally.... you might not want to turn the wheel while it's up in the air.... it might cause the blocks to slip out.

If you can.... see how far your shocks have before they hit the bump stops..... this will let you know if your close to the maximum suspension travel.

Ok.... once you have the tires in these three positions.... I would measure the clearance on all areas of the tire and write them down.

These measurements will allow you to get a good idea of how wide the tire can be.... and where it must be positioned relative to the center of the suspension/brake mounting point.

If you got these dimensions I could help you figure out the exact offset and width you can go with.

Hmmmm..... your doing a "wide body" kit right???

I'm assuming your going to cut out part of the inner and outer stock fenders so that you get more wheel clearance.... am I right????

How'd you figure out the radius? It's been way to long since I've done math. How much would 3 degrees of camber push a 255/40/17 tire?...thats a diameter of 25.03

Before I pick that exact offset wheel I need I need to figure out about what I'll be running so we can do the fenders now. I'm probably going with a 17x9 +15 for the track since I found a wheel in that size only (or +35) thats only $220 each and weight 17.5lbs each. The +15 is 11mm more clearance on the inner fender than my current 17x7.5 which with a 205/40 tire dont rub the struts at all. Push the top of the tire in 15mm and it probably will...but if that happens I can get 3mm spacers easy.

Wouldn't it also be better to just put all four wheels about 8" off the ground then do what your talking about with the measurments? cuz If the shocks compressed then the measurments would be kinda off. Compare that too taking measurments of how the car sits normally then seeing how much the shocks compress.

[PrecisionBoost]

The whole idea of measuring the clearance is to compress the shocks as much as possible...... which is exactly what happens when you hit a bump or push into a corner really hard.

Basicly you have to try and get the suspension to push up as far as it can..... then take measurements.

I'm not 100% sure of what you mean by putting all four wheels 8" off the ground.... that would make the suspension sit exactly as it would if the car wasn't jacked up at all.

The idea of jacking one side way higher is to force the weight onto the opposite side.... which compresses the suspension..... which is where your going to run into clearance problems.

It doesn't matter if it clears when sitting still..... the last thing you want is to dive into a corner an have the tire hit something inside your fender and make the car hop in the air.... which may lead to loss of control.

If it was me doing this.......... I'd fabricate some wood templates to simulate the tire diameter, width, offset and change it until everything was perfect.... then I'd order my tires/rims


The radius is simply half the diameter.... so if a 255/40/17 has a diameter of 25.03 then the radius is 12.515

With 3 degrees that moves the tire inwards 0.656"

One thought here..... I don't know what your "original" camber is in the first place.... basicly I'm assuming your moving it 3 degrees further to gain more grip.


As far as those tires are concerned..... I have to wonder if you going to manage to squeeze 255/40/17 under there..... that's 2" wider diameter than stock.

I would be more concerned about this dimension than the effects of camber adjustment.

Personally..... I'd go with 245/35/17 which are only 23.8" in diameter.... which is reasonable compared to stock.

With 2" wider diameter it's going to throw your speedometer off big time.

I know 245/35/17 aren't a common tire.......... what type of tire were you looking to put on there??

[kinkyllama]

The whole idea of measuring the clearance is to compress the shocks as much as possible...... which is exactly what happens when you hit a bump or push into a corner really hard.

Basicly you have to try and get the suspension to push up as far as it can..... then take measurements.

I'm not 100% sure of what you mean by putting all four wheels 8" off the ground.... that would make the suspension sit exactly as it would if the car wasn't jacked up at all.

The idea of jacking one side way higher is to force the weight onto the opposite side.... which compresses the suspension..... which is where your going to run into clearance problems.

It doesn't matter if it clears when sitting still..... the last thing you want is to dive into a corner an have the tire hit something inside your fender and make the car hop in the air.... which may lead to loss of control.

If it was me doing this.......... I'd fabricate some wood templates to simulate the tire diameter, width, offset and change it until everything was perfect.... then I'd order my tires/rims


The radius is simply half the diameter.... so if a 255/40/17 has a diameter of 25.03 then the radius is 12.515

With 3 degrees that moves the tire inwards 0.656"

One thought here..... I don't know what your "original" camber is in the first place.... basicly I'm assuming your moving it 3 degrees further to gain more grip.


As far as those tires are concerned..... I have to wonder if you going to manage to squeeze 255/40/17 under there..... that's 2" wider diameter than stock.

I would be more concerned about this dimension than the effects of camber adjustment.

Personally..... I'd go with 245/35/17 which are only 23.8" in diameter.... which is reasonable compared to stock.

With 2" wider diameter it's going to throw your speedometer off big time.

I know 245/35/17 aren't a common tire.......... what type of tire were you looking to put on there??

Well I said jack all four corners up 8" so I could get under it...take measurments of clearance then take measurments of the bump stops and calculate it. By jacking up only one wheel 8" off the ground it doesnt really put all that much weight on that one tire as stiff as my car is.


Can't, I'm looking at 245/35/17 for a street tire and theres only one tire in that size. I'm looking at the RA-1 which comes in either 235/40/17 or 255/40/17. Ideally I'd want a 245mm tire and even better with the 35% sidewall but thats not possible.

[PrecisionBoost]

Did you ever think about going up to 18" ??

There are a fair number of 245/35/18 , 255/35/18 , 265/35/18 tires on the market.

The 245/35/18 gives a diameter of 24.8".... which is still large... but closer than the 255/40/17.... and they are available in race tire format..... TireRack has both the Hoosier A6 and R6 in that size.

I'm not sure about the Toyo RA-1....... try these guys.......

Jonathan Nguyen

DNJ Wheels
11602 Knott Ave Unit 6

Garden Grove CA 92841

714-799-7126
714-799-7216
FAX:714-799-7540
www.DNJWHEELS.COM
www.XAUTOWHEELS.Com
Hours:10am-6pm M-F 11am-5pm Sat Closed Sunday All Times Pacific Standard


I just bought some Toyo T1-R tires for my 18" Centerline Forged rims..... and his pricing was really good.

If I remember correctly they didn't show the RA-1 on the site...... but I'm sure he can get them if he's selling Toyo tires.

As far as companies go...... these guys has some of the best communication I've seen in quite a while..... all my emails were answered quickly and there was no bullshit.... he laid it out nice and simple and cut me a deal on a package.

I also dropped a few grand on a set of 20" rims and peformance tires for my wife's Mazda CX7.

[kinkyllama]

Did you ever think about going up to 18" ??

There are a fair number of 245/35/18 , 255/35/18 , 265/35/18 tires on the market.

The 245/35/18 gives a diameter of 24.8".... which is still large... but closer than the 255/40/17.... and they are available in race tire format..... TireRack has both the Hoosier A6 and R6 in that size.

I'm not sure about the Toyo RA-1....... try these guys.......

Jonathan Nguyen

DNJ Wheels
11602 Knott Ave Unit 6

Garden Grove CA 92841

714-799-7126
714-799-7216
FAX:714-799-7540
www.DNJWHEELS.COM
www.XAUTOWHEELS.Com
Hours:10am-6pm M-F 11am-5pm Sat Closed Sunday All Times Pacific Standard


I just bought some Toyo T1-R tires for my 18" Centerline Forged rims..... and his pricing was really good.

If I remember correctly they didn't show the RA-1 on the site...... but I'm sure he can get them if he's selling Toyo tires.

As far as companies go...... these guys has some of the best communication I've seen in quite a while..... all my emails were answered quickly and there was no bullshit.... he laid it out nice and simple and cut me a deal on a package.

I also dropped a few grand on a set of 20" rims and peformance tires for my wife's Mazda CX7.

I considered it...much much less choices in 18" than 17". Plus no RA-1s in my size. The hoosiers are the last tire I want, very expensive, and dont last long at all. I'd only consider them if I was doing time attacks for some good money or lots of a fame. If I wanted to move up from the Ra-1 I'd only go with the V710 which is almost as sticky as the hoosier but lasts much longer and is a bit cheaper. Also the hoosiers are known to be bigger than stated...so a 245mm hoosier is probably the same or close to the size of a 255 anything else.

I'm gonna try to stick the 255/40/17 toyos on there... I already bought the wheels/tires. If I can't get them to fit its not a big deal as I can sell these wheels and tires quickly as they are very popular. If the tires dont fit I'll probably move down to the 235/40/17 ra-1 and if I can still keep the 17x9s. I think 255 is a bit more grip than I need but 235 is a bit less. If I ever get really competitve I'm moving over to the khumo 710 in a 245/35/18.

[PrecisionBoost]

Well.... your not the only one with bigger tires.... I screwed up and ordered 225/40-18 Toyo T1R tires instead of 215/35-18 tires.

So my diameter is pretty close to 25 inches as well.

Oh well.... I guess it gives me an excuse to fabricate some fibreglass "flared" fenders ( like the ones I'm working on for my Lemans )