gen 3 convertible rear caster adjustment and spec

[Jumbus]

Dear all,
I am writing to you from a small country called Croatia and would kindly ask for your help.
Based on the community info i have installed a moton clubsport coilover system to my gen 3. The first aligment shop did a bad job so i took the car to another shop. I took some values from this forum and decided to go with front camber -1,5 each front toe zero . Caster around 5. Rear camber -1 each rear toe in by 1,8 mm each.

now my magic two questions. What is the rear caster spec for gen 3 and is it valid with moton clubsport and ps2 tires?

How can i adjust it without using the factory inclinometer and adapters?

I need some diy solution because here at the seaside is no dealer.

any idea out there? And yes i am wiling to play mcgyver because no choice.

Kind regards

Ivo

 

[Jumbus]

Cant believe nobody in this forum knows it?

 

[RolandDV]

I Always used a DRB III and the inclinometers. I know some alligning equipment from Beissbarth has the EU spec Viper in the software. Doing this yourself without equipment is nearly impossible to get it wright in my opinion.

 

[Jumbus]

Hi Roland. Aligning equipment is not the problem for front caster but none of the equipment i know can adjust rear caster. Or am i wrong?

 

[MoparMap]

I didn't think the rear had much for a caster setting. The upper control arms don't have cam bolts, so they aren't really adjustable. You can get some caster with the lower adjustment, but it will change camber as well. When I got my car aligned several weeks back they didn't even have a readout for the rear caster, just camber and toe. The caster wouldn't really matter that much anyway because the wheels aren't turning side to side, so you don't get the dynamic camber change you see on the front.

 

[Tom Sessions]

Rear caster is huge on the cars. A regular alignment rack won't give you a rear caster read out. You have to use the DRB with the inclinometer. If you don't have a shop with the right equipment the best rule is to have the rear cams on the lower control arms clocked in the same direction. You don't want one cam at 3oclock and the other cam at the 9 oclock position. You can get the correct camber reading like this but it changes caster and results in a ill handing car.

 

[Jumbus]

Hi Tom this is exactly what i did. Rear cams on the lower control arm are set on the same direction. I hope this accurate enough.

 

[Jumbus]

Does anyone know the rear caster spec?

 

[Viper X]

Wish I could help.

Never needed to adjust rear caster on any Viper.

Manual would likely have the answer.

Dan

 

[Jumbus]

Dear All,

My manual does not give me the answer unfortunately. I have one idea which is a very rough estimation but maybe helpful:

Can someone please tell me the distance between rear fender (plastic) and rear tyre? I have 6cm on both sides.
Gen III 06 convertible.

Best regards,
Ivo

 

[NO HEMI]

Mark @ woodhouse gave me the specs for my car and it's a totally different beast now , it just swallows the curves!!!, i think you should ask him. he'll probably be able to help you.

 

[Jumbus]

Ok thank you. Mark are you reading this???
Please help.

 

[MtnBiker]

I just had my Gen IV aligned with a "mild" track alignment. Front toe 0.1, front camber -1.2 and caster 6.5. Rear toe 0.1, rear camber -1.5. No caster in the rear.

 

[Jumbus]

Hi Mtn Biker,

Are the rear cams on the lower control arm set on the same direction/ angle?
What is the distance between rear fender (plastic) and rear tyre? I have 6cm on both sides.

Best regards,
Ivo

 

[Jumbus]

Hello Everyone,

according to this page
http://www.handsontools.com/Miller-Tools-8996-Rear-Casters-Adapters-_p_36043.html
I need those adapters and the 9689 Inclinometer, 6996 Inclinometer Switch Box and DRBIII.

It seems to me some of you did not go by the book and adjust rear caster as above. So how critical is this point?
Can someone with a factory rear caster adjustment tak a look and check the position of their rear cams on the lower control arm?
Just the first info if both stay parallel (same direction) or not. It will be a good hint for me.

Almost cant believe this topic is not interesting to more people.

Best Regards,

Ivo

 

[MtnBiker]

Hi Mtn Biker,

Are the rear cams on the lower control arm set on the same direction/ angle?
What is the distance between rear fender (plastic) and rear tyre? I have 6cm on both sides.

Best regards,
Ivo

Ivo,

Just saw this. I will take measurements and get back to you. Can't answer your first question as I honestly don't know what the heck it means?!

 

[mjorgensen Woodhouse]

Hello Everyone,

according to this page
http://www.handsontools.com/Miller-Tools-8996-Rear-Casters-Adapters-_p_36043.html
I need those adapters and the 9689 Inclinometer, 6996 Inclinometer Switch Box and DRBIII.

It seems to me some of you did not go by the book and adjust rear caster as above. So how critical is this point?
Can someone with a factory rear caster adjustment tak a look and check the position of their rear cams on the lower control arm?
Just the first info if both stay parallel (same direction) or not. It will be a good hint for me.

Almost cant believe this topic is not interesting to more people.

Best Regards,

Ivo

Ivo,

Sorry I missed this, but you already have great advice going in. The rear caster spec if you have the tools to do it is +.70 +/- .50 degrees. If you adjust the camber you should always move the two lower eccentrics the same amount to prevent caster from changing dramatically. It will change some though and it would be best to actually measure it.

 

[Jumbus]

Dear Mark,

Thank you for the spec data.
+.70 +/- .50 degrees means quite a lot of margin. Do you know which one of the eccentrics on the lower arm must be turned more to get the caster slightly above 0?
(which side of the lower control arm needs to be turned more towards "in" position?, first or second from driving direction)

If I assume parallel setting of eccentrics mean 0 caster then I could turn the one (you tell me which one please ;-) little more and hope to be within +.70 +/- .50 degrees.

@MtnBiker: Maybe you understand my question now?

Best regards,

Ivo

 

[mjorgensen Woodhouse]

Dear Mark,

Thank you for the spec data.
+.70 +/- .50 degrees means quite a lot of margin. Do you know which one of the eccentrics on the lower arm must be turned more to get the caster slightly above 0?
(which side of the lower control arm needs to be turned more towards "in" position?, first or second from driving direction)

If I assume parallel setting of eccentrics mean 0 caster then I could turn the one (you tell me which one please ;-) little more and hope to be within +.70 +/- .50 degrees.

@MtnBiker: Maybe you understand my question now?

Best regards,

Ivo

Without measuring your current caster you cannot insure you are going the correct way with the settings, but as a general rule if you rotate the eccentrics to move the wheel further forward in the wheel well you are increasing caster.

 

[Jumbus]

Dear Mark,

Do you know where I can buy the complete tool set to adjust rear caster and how much does it cost?
I have just found some parts on ebay but not the complete set.

Can you provide it to me?

Best regards,

Ivo

 

[mjorgensen Woodhouse]

Dear Mark,

Do you know where I can buy the complete tool set to adjust rear caster and how much does it cost?
I have just found some parts on ebay but not the complete set.

Can you provide it to me?

Best regards,

Ivo

You would need a DRB, do you already have one of those?Pricey if you can find one, I know we can order the hard parts, but would needto find pricing if you have the DRB.

 

[Jumbus]

Dear Mark,

No DRB but I have a SCT Tuner. Can it do the job?
Best regards,
Ivo

 

[mjorgensen Woodhouse]

Dear Mark,

No DRB but I have a SCT Tuner. Can it do the job?
Best regards,
Ivo

No the SCT won't have the information in it sorry.

 

[Jumbus]

It is frustrating I do need a DRB for this adjustment. Honestly speaking I can not understand why. At the moment I can not find a solution ;-(

 

[Mopar Steve]

The relationship of the upper and lower ball joint on the upper and lower control arm is what will change caster. Doing this old school can get you very close. You can use a level against the upper and lower control arm and measure for plumb. be sure that both sides are the same and you will be very close.

 

[Jumbus]

Hello Steve,

Your idea is very interesting to me. I do not understand it completely. Would you mind to explain it step by step to me?.
My understanding is that upper control arm joints are fixed and can not be adjusted but caster setting is done by adjusting the eccentrics on only the lower arm.

car needs to be on leveled ground i suppose? if upper and lower arm are plumb then caster is zero? i need little positive caster as described above.

Best regards,

Ivo

 

[Dan Cragin]

Rear caster is has to be set correctly or the car will be dangerous. We learned a lot with the rear steer Gen 1 cars, thus the big change in 1996 to the suspension and alignment. Your can measure rear caster with a gauge, Longacre has the tool, you just need to make a couple mounting tabs.

We prefer to run a lot of caster in the front, the new Gen 5 Viper is a good example. Right from the factory it has a track ready setup with 7 plus degrees of caster in the front and lots of negative camber both front and rear. More caster in the front gives more mechanical grip, it also slows down the steering, allowing you to make toe changes that improve response.

Hope this helps.

 

[Jumbus]

Dear Dan,

Car is Gen3.

according to upper opinions Gen3 rear caster needs DRB to be measured.
Are you sure I only need a gauge for Gen3 rear caster adjustment? That would be great news for me.
If so then which gauge is it and how to use?

Front caster is no issue, every aligning machine can do it.

Best regards,

Ivo

 

[Dan Cragin]

You need to make some custom mounts to attach the gauge to the rear suspension. I would use it back in the day at the track when we had to make changes using chalk and string, let me see if I can drag it out and reproduce it.

 

[Jumbus]

Dear Dan,

It would be great if you also could make a drawing or so.
Im not sure if the club members are aware of this item, from reading many posts i have the feeling most of the people just take the car to a normal alignment shop which does not care about the rear caster.