Ride height/alignment question

[JD Cross]

I have not posted on this before and looking for some help.
My 91 is stock with 15/16 wheels.
I have collector plates on my car which permits lowering by an inch but requires retaining oem wheels (+/-two years)

It looks like it's time to replace my dampers.
I have a set of low mileage oem 98 dampers with Tein-S-Tech springs mounted on them which would lower the car about an inch I.

My question centers on wheel offset when you lower an NSX.
My understanding is at oem height the rear suspension arms are parallel to the ground and the wheel is at it's outermost position.
As the suspension moves up or down the suspension arms go through an arc which pulls the wheel more inboard.
This means lowering the car changes the suspension arm angle so the wheels are all pulled inboard by some amount.
Is it a significant amount?

As the oem wheel position sets the wheels fairly inboard, I'm concerned lowering my car will make it look worse.
Is the solution here to put some small spacers behind the oem wheels to pull them out?

I'm aware lowering requires re-alignment

 

[NSX-Files]

Lowering it 1" will not tuck the wheels in close by that much. But yes, spacers will help the wheels stick out more to keep them from looking too anemic. But will also affect the crisp handling a little. If you use spacers, I'd suggest a 10mm differential (i.e., the rear spacer being 10mm thicker than the front one). This balances the look since the rear wheel is inset more than the front.

 

[JD Cross]

Lowering it 1" will not tuck the wheels in close by that much. But yes, spacers will help the wheels stick out more to keep them from looking too anemic. But will also affect the crisp handling a little. If you use spacers, I'd suggest a 10mm differential (i.e., the rear spacer being 10mm thicker than the front one). This balances the look since the rear wheel is inset more than the front.

Now another question.
NSX oem wheels are 55 mm front and 60 mm rear positive offset.
Doesn't that mean the rear wheels are 5 mm more to the outside?
I am not knowledgeable in this at all.

When you install a spacer I presume you replace the wheels studs with longer ones?

 

[Stephen@NCAutoUSA]

Depends on what mm spacer. I was always told 3mm is fine with stock studs and some push 5mm but that's with aftermarket wheels of 8 front and 9-10 rear. I'm not sure if width of the wheel matters but I'd assume not all bolt holes are the same thickness so to answer your question, I think it just depends on how many revolutions you have when you put on a spacer and have the lug nut on hand to really test.

I wouldn't worry about a spacer on oem wheels truthfully. They're already inward and lowering your car 1 inch like mentioned above won't change anything drastically, and I thought as well an alignment can dial that out. Now if you go lower then it may be an issue.

 

[NSX2398]

I also have a '91 with both 15/16 wheels and later 16/17 OEM wheels. There are two kinds of spacers .. ones that are just spacers (typically thinner ones) without their own lugs .. and those that are thicker and have their own integrated lugs. If you use the first type, you have to make sure that you are left with enough lug threads .. which you can find if you search threads or maybe in the Wiki. If you don't have enough threads, then you'll have to install longer lugs. The latter kind basically bolt onto the wheel using the OEM lugs and the nuts are recessed into the spacer. You then bolt your wheel to the new lugs/nuts that came with the spacer. The new lugs are offset (rotated) by half the distance between two OEM lugs so they don't interfere .. and if the OEM lugs protrude beyond the outside face of the spacer, it's usually ok because most wheels have a hollow space behind the spoke. However, my front 15" OEM wheels won't work with the 16mm spacers I use for the front 16" wheels ... and IIRC, the problem is that the OEM 15" wheels don't have enough of a hollow behind the spokes. If I was using a thicker front spacer (like 25mm), it would probably work. But I think the general consensus is that a 15mm or 16mm front spacer and a 25mm rear one brings both the front and rear out flush with the wheel wells. And if you use Bilsteins on the lower perch, which lowers the car about 3/4", they still look good.
According to this Wiki page, you need at least 6 full lugnut turns if you're using the first kind of spacer (scroll down to the spacers section): http://nsxprime.com/wiki/Wheel-Tech-Aftermarket

 

[JD Cross]

Many thanks to all who posted
I think I understand how this works now. :smile:

 

[Larry Bastanza]

JD,

My car has been lowered for the last 12 years with Eibachs, OEM 15/16" wheels. Just a fresh alignment and you are good to go. Frankly I would not recommend the Eibachs, since they have sagged alot over this time period, but the Teins seem to be much better.

HTH,
LarryB

 

[Honcho]

Time for BC Racing, Larry. Love em'.

 

[2000NSXT]

Larry, do you have any experience with H&R Sport springs? Would you recommend them over Eibachs?

 

[nsxtasy]

NSX oem wheels are 55 mm front and 60 mm rear positive offset.
Doesn't that mean the rear wheels are 5 mm more to the outside?

No. As shown in these diagrams, the offset is the distance between the center plane of the wheel and its mounting surface (which joins the mounting surface of the hub). Because the NSX wheels have positive offset, that means the effect of the offset is that the outer faces of the rear wheels actually are more to the inside of the car, not the outside. However, that doesn't mean that the rear wheels are more to the inside overall; they may be more flush (more to the outside) if the suspension geometry is such that the mounting surface of the rear wheels (the hub surface) sticks out more, enough to offset the difference caused by the difference in offset between the front and rear. Hope that makes sense.

I think it just depends on how many revolutions you have when you put on a spacer and have the lug nut on hand to really test.

FWIW, I've read various recommendations that the lug nuts have 6, 6.5, or 7 full turns to keep the wheels on.

 

[Hapa88]

I have not posted on this before and looking for some help.
My 91 is stock with 15/16 wheels.
I have collector plates on my car which permits lowering by an inch but requires retaining oem wheels (+/-two years)

It looks like it's time to replace my dampers.
I have a set of low mileage oem 98 dampers with Tein-S-Tech springs mounted on them which would lower the car about an inch I.

My question centers on wheel offset when you lower an NSX.
My understanding is at oem height the rear suspension arms are parallel to the ground and the wheel is at it's outermost position.
As the suspension moves up or down the suspension arms go through an arc which pulls the wheel more inboard.
This means lowering the car changes the suspension arm angle so the wheels are all pulled inboard by some amount.
Is it a significant amount?

As the oem wheel position sets the wheels fairly inboard, I'm concerned lowering my car will make it look worse.
Is the solution here to put some small spacers behind the oem wheels to pull them out?

I'm aware lowering requires re-alignment

Jim,
Adrian H. here from the FB page. A few things to note here. The OEM 98 dampers are slightly different from the 1991 dampers. Since they are designed for the NSX-T, the have slightly different damper rates.

From the NSX Wiki "At low rates of wheel travel, T front rebound and compression rates are 7% softer. At higher rates, T rebound is 21% softer, compression is 32% softer. At high rates, T rebound is 15% softer, compression is 21% softer."

People have found that by replacing the 1991-1994 dampers with 1995 & up dampers that their cars end up sitting higher than before. I assume that has something to do with the dampers/springs, rates and/or difference in curb weights.

That being said, you may be better off keeping the OEM springs and using the Bilstein aftermarket struts. They have a lifetime warranty and give you the option of having them at the OEM height or a drop of ~7/8" by selecting the different perches.

Because of the suspension geometry of the NSX, when you lower the car, it tends to pull the wheels inward, as highlighted by these two pictures.
<img src="http://www.nsxprime.com/photopost/data/500/Raised.jpg" />
<img src="http://www.nsxprime.com/photopost/data/500/NoSpacer.jpg" />


As for your offset question. "NSX oem wheels are 55 mm front and 60 mm rear positive offset. Doesn't that mean the rear wheels are 5 mm more to the outside?"
Wheel position relative to the fender is a function of both offset AND wheel width. So if the front wheel (15x6.5 +55) were mounted rear, it would actually appear 14mm more inward than the rear wheel would normally sit.
14mm is because of the 1/2 the wheel width difference of 1.5" minus the 5mm difference in additional positive offset. You can use this calculator to help you.
http://www.1010tires.com/Tools/Wheel-Offset-Calculator

 

[JD Cross]

Jim,
Adrian H. here from the FB page. A few things to note here. The OEM 98 dampers are slightly different from the 1991 dampers. Since they are designed for the NSX-T, the have slightly different damper rates.
From the NSX Wiki "At low rates of wheel travel, T front rebound and compression rates are 7% softer. At higher rates, T rebound is 21% softer, compression is 32% softer. At high rates, T rebound is 15% softer, compression is 21% softer."
People have found that by replacing the 1991-1994 dampers with 1995 & up dampers that their cars end up sitting higher than before. I assume that has something to do with the dampers/springs, rates and/or difference in curb weights.
That being said, you may be better off keeping the OEM springs and using the Bilstein aftermarket struts. They have a lifetime warranty and give you the option of having them at the OEM height or a drop of ~7/8" by selecting the different perches.

Adrian
Thank you for this info.
I wasn't aware the damping rates were different on 98 vs. 91 dampers.
The Tein S-Tech springs mounted on the dampers are both stiffer than the 91 oem springs and shorter by about 1"
I felt this combo would be giving me a slightly firmer lower suspension but perhaps not.
Could you comment on this?
Jim

 

[Hapa88]

Adrian
Thank you for this info.
I wasn't aware the damping rates were different on 98 vs. 91 dampers.
The Tein S-Tech springs mounted on the dampers are both stiffer than the 91 oem springs and shorter by about 1"
I felt this combo would be giving me a slightly firmer lower suspension but perhaps not.
Could you comment on this?
Jim

Jim, I can't with 100% confidence tell you if that setup will achieve your goals lowering goals. LarryB may be able to shed some light

What I can tell you is that the part numbers are, in fact, different and if you do some digging on NSXPrime you may find the posts of the people having those ride height issues I mentioned previously.

Take the front suspension parts for example.
1991: http://www.hondapartsunlimited.com/...hock-absorber/?trim=nsx&engine=5-speed-manual
1998: http://www.hondapartsunlimited.com/...ck-absorber/?trim=nsx-t&engine=6-speed-manual

Front Strut kit
1991 - part# 06511-SL0-950
1998 - part# 06511-SL0-601

Front Spring
1991 - # 51401-SL0-013
1998 - # 51401-SL0-601

I can tell you that I had the Bilstein struts with my OEM springs on my 1991 NSX and I loved it. Others, like nsxtasy, also like that setup. I have read one review, however, that didn't care for it and the guy compared multiple suspension setups he tried.

EDIT: Found a link of people running later model struts on early model NSXs.
http://www.nsxprime.com/forum/showthread.php/141217-QQ-on-struts-and-springs-compatibility-03-gt-91

 

[JD Cross]

Adrian

Here's the data I have:
91 oem front damper compression rate 98 rebound 101
98 oem front damper compression rate 109 " 115

91 oem rear damper compression rate 112 rebound 173
98 oem rear damper compression rate 125 " 183

This would suggest the 98 dampers would feel firmer.

The spring rates are as follows:
91 oem front 170 rear 220
Tein S-Tech front 224 rear 246
Ride height difference Tein S-Tech is front .7 " shorter and rear 1.0" shorter.
So the Tein springs should set the ride height .7-1.0" lower due to spring length and be firmer than the oem springs.

Does this make sense?

 

[Hapa88]

Adrian

Here's the data I have:
91 oem front damper compression rate 98 rebound 101
98 oem front damper compression rate 109 " 115

91 oem rear damper compression rate 112 rebound 173
98 oem rear damper compression rate 125 " 183

This would suggest the 98 dampers would feel firmer.

The spring rates are as follows:
91 oem front 170 rear 220
Tein S-Tech front 224 rear 246
Ride height difference Tein S-Tech is front .7 " shorter and rear 1.0" shorter.
So the Tein springs should set the ride height .7-1.0" lower due to spring length and be firmer than the oem springs.

Does this make sense?

Jim, where did you get the data on the rates? They completely contradict the NSXWiki information on the Targa's and all the articles I've read about the changes. Unless you have the 1998 "Coupe" suspension?
http://www.nsxprime.com/FAQ/General/modelinfo/modelinfo.htm

 

[JD Cross]

Jim, where did you get the data on the rates? They completely contradict the NSXWiki information on the Targa's and all the articles I've read about the changes. Unless you have the 1998 "Coupe" suspension?
http://www.nsxprime.com/FAQ/General/modelinfo/modelinfo.htm

Adrian
I found spring and damper rates rates here:
http://www.nsxprime.com/wiki/Suspension
Jim

 

[Hapa88]

Adrian
I found spring and damper rates rates here:
http://www.nsxprime.com/wiki/Suspension
Jim

Yeah, I guess I have the same questions. The Suspension rates table don't specify whether they are NSX-T or NSX Coupe rates which are different. I guess if you already have all the parts, go ahead and try it? I'm sure you'll see an improvement just with the newer struts..

 

[JD Cross]

Yeah, I guess I have the same questions. The Suspension rates table don't specify whether they are NSX-T or NSX Coupe rates which are different. I guess if you already have all the parts, go ahead and try it? I'm sure you'll see an improvement just with the newer struts..

I'm putting the dampers and springs in next week .
I'll let you know how the cars feels after.

 

[Hapa88]

I'm putting the dampers and springs in next week .
I'll let you know how the cars feels after.

Let us know if the height changes any too.

 

[JD Cross]

Let us know if the height changes any too.

The 98 T- dampers and Tein S-Tech springs are on now.
The car is about 1" lower which looks better.
It feels like T dampers have a firmer compression rate compared to the 91 OEM dampers, likely because they are rated for a slightly heavier car.
The springs are slightly firmer too.
The car feels tighter all round and the ride is not tooth rattling.
I think this is a good low cost suspension refresh.

 

[Hapa88]

Good info and I'm glad you're happy with the results.
Just to be clear though; when you're comparing the firmness, are you referring to the worn 1991 OEM dampers that you just removed to the lightly used 98-T dampers that you just put in?

 

[JD Cross]

Good info and I'm glad you're happy with the results.
Just to be clear though; when you're comparing the firmness, are you referring to the worn 1991 OEM dampers that you just removed to the lightly used 98-T dampers that you just put in?

Yes I'm comparing my 100k mile 91 oem set to the 35 k mile 98 oem set.
I might just be observing the feel of newer dampers and springs :smile: