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Wheel Offset and Spacers, Set Up Numbers

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#1
bmarshall1

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Currently I have 30 offset wheels, I understand that we can go as low as 25 and be legal.  From what I understand the 99 had a track difference of 1 inch f/r in order to help eliminate oversteer (rear is wider).

 

I understand the benefit would be negligible, if any; but would there be any negatives to adding spacers to the front only in order to get closer to equal tracks f/r and would there be any other changes one may want to make to go along with this as well.  Or, is the SPEC suspension set up taken all this into consideration and I would be upsetting a finely balanced machine. :D

 

Mind you I am mid pack (ok, ok, lower 1/3 pack, alright... almost last :whistling:

 

But my OCD really wants the track to be closer

 

I don't have current caster/camber settings as I am going through the suspension and replacing bent parts.  Any set up numbers are appreciated, it will be a set and forget, I am still running Bilsteins until I get Penske funds.

 

I believe I was running about 3.2/2.7 f/r camber, 4 5/8 f, 4 3/4 r ride height, slight toe out front and slight toe in rear, (maybe 1/8 total) and this was a fairly neutral set up for me.

 

Thoughts?


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#2
Tom Sager

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You'll get a variety of opinions on this but I wouldn't mess with spacers at this point.  Your alignment IMO could be a lot better.  You might consider running more like negative 3.8 degrees camber front and negative 3.5 degrees rear (If you can get that much rear).  If you don't have offset bushings yet in front upper control arms, suggest you install those.  For front toe more like 3/16" out total and just a smidge toe-in at each rear wheel.  I'd also suggest lowering your rear ride height to be the same as front if you're using pinch weld measurements and if they are in good measurable shape.  This should be a generally competitive alignment setup and probably closer to what those in front of you are running. 


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#3
bmarshall1

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Hi Tom and thank you.  I have always been to the understanding that a slight amount of rake is good, but I'll try to lower the rear a bit.  If I am correct, it will keep the rear planted a bit more under braking and help the rear hook up under corner acceleration - perhaps promote a bit of understeer?

 

Do you prefer the offset bushings over extended ball joints.

 

Also, my pinch welds are pretty bad, can I use the space between the top of the shock body and the bump stop to the same effect (say 3/4 gap?), I am still running Bilstiens.

 

Thanks for all the help.



#4
Alberto

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Extended ball joints are easier to install imo.  Some people worry about the bushings slipping but YMMV.  When you install the extended ball joints, you'll probably wind up with ~5* camber so be ready to re-adjust.  

 

My pinch welds look like they've been chewed by rabid dinosaurs.  I have yet to see a car with pinch welds that are consistent enough to be used as measuring points so this concept of ride height eludes me. :)

 

You probably won't be able to get 3/4" gap at the bump stop on the driver rear and get a low ride height.  Most of the driver's weight is on that corner.  Most people say a finger's width (insert reference Frank's finger - joke).  Some make reference to being able to comfortable insert a 3/8" drive extension between the shock and bump stop.  I've been aiming for a bit over the width of my 3/8" extension (so 3/8-1/2) and it's been serving me well.  I don't like being on the bump stops too much.  

 

I also aim for about 3.5-3.8* front camber.  I also found that my 1.6 car feels better with ~3.5* rear camber.  I used to run about 2.75-3 then increased to -3.25 and then again to -3.5 and the extra camber and increased bump stop gap at the driver rear shock has really helped.  The car sticks a lot better and is more forgiving at the limit.  Especially in T3 and T5a at Thunderhill for example.

 

hth...


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#5
bmarshall1

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Extended ball joints are easier to install imo.  Some people worry about the bushings slipping but YMMV.  When you install the extended ball joints, you'll probably wind up with ~5* camber so be ready to re-adjust.  

 

My pinch welds look like they've been chewed by rabid dinosaurs.  I have yet to see a car with pinch welds that are consistent enough to be used as measuring points so this concept of ride height eludes me. :)

 

You probably won't be able to get 3/4" gap at the bump stop on the driver rear and get a low ride height.  Most of the driver's weight is on that corner.  Most people say a finger's width (insert reference Frank's finger - joke).  Some make reference to being able to comfortable insert a 3/8" drive extension between the shock and bump stop.  I've been aiming for a bit over the width of my 3/8" extension (so 3/8-1/2) and it's been serving me well.  I don't like being on the bump stops too much.  

 

I also aim for about 3.5-3.8* front camber.  I also found that my 1.6 car feels better with ~3.5* rear camber.  I used to run about 2.75-3 then increased to -3.25 and then again to -3.5 and the extra camber and increased bump stop gap at the driver rear shock has really helped.  The car sticks a lot better and is more forgiving at the limit.  Especially in T3 and T5a at Thunderhill for example.

 

hth...

 

Thanks for the info Alberto - I am going through my car from end to end and refurbing/updating as needed and will apply your comments as applicable.   I'm going to try for 3.8 - 3.5 camber up front w/o the EBJ, we'll see how that works out.

 

I also read your write up on engine rebuild, very good write up.  Question:  It seems you were a few HP over the limit for your class, I assumed you adjusted the timing to get more torque in place of lower HP?  The question is do you feel you gave up much HO/TQ by doing it yourself vs. going to an engine builder, or, would it not have mattered due to the HP limit?

 

Lastly - I met Frank once years ago at Mid Ohio, nice guy but I don't think I want his finger anywhere near my car, who knows where it has been. :butthead:

 

(just kidding Frank, you and your brother? treated me very nice).


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Tom Sager

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Hi Tom and thank you.  I have always been to the understanding that a slight amount of rake is good, but I'll try to lower the rear a bit.  If I am correct, it will keep the rear planted a bit more under braking and help the rear hook up under corner acceleration - perhaps promote a bit of understeer?

 

Do you prefer the offset bushings over extended ball joints.

 

Also, my pinch welds are pretty bad, can I use the space between the top of the shock body and the bump stop to the same effect (say 3/4 gap?), I am still running Bilstiens.

 

Thanks for all the help.

Finger measurement varies from finger to finger.  I think 3/4" is about right, maybe slightly less.  With Bilsteins the chances of getting too deep into the bump stops with much less than that increases.  Haven't tried the ball joints but have had an offset bushing turn a bit. Pinning them somehow is probably advised. 

 

You haven't mentioned scales.  Do you scale the car? 


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#7
Alberto

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Thanks for the info Alberto - I am going through my car from end to end and refurbing/updating as needed and will apply your comments as applicable.   I'm going to try for 3.8 - 3.5 camber up front w/o the EBJ, we'll see how that works out.

 

I also read your write up on engine rebuild, very good write up.  Question:  It seems you were a few HP over the limit for your class, I assumed you adjusted the timing to get more torque in place of lower HP?  The question is do you feel you gave up much HO/TQ by doing it yourself vs. going to an engine builder, or, would it not have mattered due to the HP limit?

 

Lastly - I met Frank once years ago at Mid Ohio, nice guy but I don't think I want his finger anywhere near my car, who knows where it has been. :butthead:

 

(just kidding Frank, you and your brother? treated me very nice).

 

 

 

 

 

Regarding the engine, the region's dyno shop 'tunes' the engine to get the target HP and then seals it.  He doesn't provide details on what he does but there aren't many options that I'm aware of - add more fuel pressure to richen the air:fuel ratio and decrease HP, run less timing, adjust the air flow meter.  

 

Short answer - doesn't matter due to HP limit.  My goal was to run the sealed class in my region so I wasn't really building to hit the SM national worthy HP level.  We already knew in advance that the easy formula to hit the HP number on the 1.6 was to run a pro head on a decent bottom end.  That's typically enough to hit the ~115ish hp limit of our sealed class. 

 

If I wanted more HP out of that build, I could have gotten a pro head from one of the good SM engine builders instead of just having the machine shop freshen my head.  There are plenty of people to race in the sealed class so I haven't felt any regret at being at a HP deficit compared to the non-sealed competitors.  My car, and the other sealed cars, are a bit slower than the non-sealed, regional cars.  That class is referred to as SMT (they run Toyo RR instead of HoHos).  Some of the engines in SMT class have questionable engine legality. :)

 

That said, as I got faster, and running with some of the SMT cars, it does start to get annoying to have to work harder to pass the out of class cars with more HP.  Then again, I don't get out consistently enough so it basically only matters if I am able to run a full season and get enough seat time for the skills to come back to my old level and then improve to make it further up the field.   

 

Fundamentally, you want to be on par HP level aka parity with the people around you.  For the guys running nationals and what not, that's 120+hp pro motors and the corresponding budget.  For those of us not at that level...

 

Part of my reason to rebuild my engine was simply to challenge myself and learn something new.  It was fun and my goals were met.  I will probably do another one and this time do the oversized pistons and pro head so I can get closer to the pointy end.  We'll see how this covid crap and the economy goes in the next year.  Right now, I'd just be happy to get to the track, drive, race and bs with my racing buds safely.


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#8
Steve Scheifler

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Alberto, the point being made is that tuning just to a peak HP number leaves open lots of possibilities to optimize total power available through the usable RPM range. Power curves are just that, curves, not linear, so you can tinker with a tune to get more power/torque throughout the RPM range you use during racing without exceeding the peak limit set by rules. It is potentially huge in lap times.
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#9
Alberto

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Alberto, the point being made is that tuning just to a peak HP number leaves open lots of possibilities to optimize total power available through the usable RPM range. Power curves are just that, curves, not linear, so you can tinker with a tune to get more power/torque throughout the RPM range you use during racing without exceeding the peak limit set by rules. It is potentially huge in lap times.

 

Ah, ok.  I obviously missed that... :)  Agreed.  

Did you have a thread on tuning the 1.6 or was that someone else?  If you have a link to that, I'd love to re-read it.


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#10
bmarshall1

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Finger measurement varies from finger to finger.  I think 3/4" is about right, maybe slightly less.  With Bilsteins the chances of getting too deep into the bump stops with much less than that increases.  Haven't tried the ball joints but have had an offset bushing turn a bit. Pinning them somehow is probably advised. 

 

You haven't mentioned scales.  Do you scale the car? 

Hi Tom - yes I scale the car, w/ driver's weight, ready to race, and 1 gallon of fuel on leveled pads.  I made a set of wire gauges of 5/8 and 3/4 lengths to measure  shock to bump stop distance.  It's been a while since I have critically looked at my pinch welds.  Rather than use the pinch weld, could one simply place a level along the pinch weld or door sill for leveling and then verify with bump stop clearance?



#11
bmarshall1

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Alberto, the point being made is that tuning just to a peak HP number leaves open lots of possibilities to optimize total power available through the usable RPM range. Power curves are just that, curves, not linear, so you can tinker with a tune to get more power/torque throughout the RPM range you use during racing without exceeding the peak limit set by rules. It is potentially huge in lap times.

Steve made my point much better that I did.  Also - I never thought about de-tuning a motor with fuel/air ratios.  I bet one could build a 'pro' motor tuned for max TQ and 'power under the curve' and still have a very strong motor, maybe?



#12
Jamz14

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I dont believe it is legal anymore in NASA to run spacers on only one end of the car. They are preventing the ability to "square" the car by running different offsets and spacers.
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#13
Tom Sager

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Hi Tom - yes I scale the car, w/ driver's weight, ready to race, and 1 gallon of fuel on leveled pads.  I made a set of wire gauges of 5/8 and 3/4 lengths to measure  shock to bump stop distance.  It's been a while since I have critically looked at my pinch welds.  Rather than use the pinch weld, could one simply place a level along the pinch weld or door sill for leveling and then verify with bump stop clearance?

Some have used only the bump stop clearance to set height.  If you can find a way to accurately measure that, then go that route.  5/8" clearance IMO is bordering on too low depending on track.  If you're too low in rear you'll get some oversteer, not that hard to diagnose.  If you're too low in front you might get more of a push than desired but it's not that dramatic, harder to determine.  Fine line, but being an eighth inch higher than perfect is better than being an eighth lower than perfect IMO. 


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#14
Steve Scheifler

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I dont believe it is legal anymore in NASA to run spacers on only one end of the car. They are preventing the ability to "square" the car by running different offsets and spacers.


Check that, it seems wrong. More likely it reads that spacers, and wheel offsets, on a given end must be the same side-to-side.
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Jamz14

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Steve, I am correct. I know this to be true as I checked on it and the specific purpose for changing the rules was to prevent exactly what this gentleman is trying to do. I'd be widening the front if I was allowed.
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Steve Scheifler

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Then someone better inform the person maintaining their rules. From the 2020 edition still online:

17.3 Track Width
17.3.1 The front shall not exceed 1450.00mm.
17.3.2 The rear shall not exceed 1475.00mm
17.3.3 Aftermarket wheel studs, lug nuts, and wheel spacers are permitted. If spacers are used they shall be no greater than 13mm in total and equal per axle.


Interestingly, the rule for wheels could use similar per axle language but instead all 4 must be dimensionally the same. That’s a PIA for someone with slightly different sets, and completely unnecessary.
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#17
Jamz14

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Steve, the rules are as I said they were and as you posted. My point was that all 4 corners have to have the same dimensions for spacers and wheel offsets. My point wasnt that you couldnt use spacers. It was that you cant use them to widen the front or reduce the rear and thereby "square the car" up. If you have to use the same gear on all four corners then you cant change the ratio of front to rear track width. Last year the rules were such that left and right had to be the same only. Meaning front and rear could be different. For whatever reason nasa didnt like that and changed it to all 4 corners had to be the same.
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#18
Jamz14

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I could have been clearer in my first post.
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#19
Steve Scheifler

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I could have been clearer in my first post.


Please read the rule again, as well as my comments about wheels. Surely the inclusion of “equal per axle” means exactly the opposite of what you are saying.
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#20
Ron Alan

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If you are correct James...then wheel offsets need to be added to any spacer wording. People have been squaring up cars for a long time...nothing new. Max front...less than max on the rear.

When the rear track width became the same for all year cars...many ran spacers on just rear axles on NA cars(still do) before the allowance of the NB upright. Of course this does the opposite of squaring...but always legal as far as I know. 


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