Jump to content
JochemsTR

Lowering front w/o changing springs

Recommended Posts

Hello,

I was on the racetrack yesterday and noticed nice TR6 next to mine...his front was slightly lower but in combination with the rear it looked really good.

My front is currently slightly higher than the rear. The guy told me he added shims between the lower wishbone and the spring pan. I looked under his car and saw about 1/4" thick washers.

The spring pan is attached by bolts. So no problem there. These need to be a little longer. However, there are two studs also. and I forgot to check how he solved the matter there.

Anyone?

Regards

Jochem

 

Edited by JochemsTR

Share this post


Link to post
Share on other sites

Hi Jochem,

I'm not a racer, but I'm pretty sure if you are only needing 1/4 "

the original studs would be long enough.

John.

Share this post


Link to post
Share on other sites

Hi Jochem,

I agree with John, with 1/4" washers you get not much lower.

Each millimeter on the TR4A-TR6 front coil springs makes the front 2 mm shorter.

I send my coil springs to a specialist who pressed them shorter, I remember 20 mm but have for the bill.

Ciao, Marco

Edited by Z320

Share this post


Link to post
Share on other sites

Hi Jochem,

I can see if you put just washers (rings) between the  spring pan and the wishbones, this will give the spring pan more freedom to start flexing which could result in fatigue. Not sure if this is a valid concern though. 

Waldi

Share this post


Link to post
Share on other sites

In my opinion the force that presses the spring is still the same, so its lengh should also be the same - with washers and without.

Share this post


Link to post
Share on other sites
7 minutes ago, Z320 said:

25 mm

Attention folks,

with this you have to use modified brackets for the shock absorbers!!!

Share this post


Link to post
Share on other sites

...or fit the lower wishbones upside down.   That drops it a bit

Share this post


Link to post
Share on other sites
1 hour ago, Z320 said:

In my opinion the force that presses the spring is still the same, so its lengh should also be the same - with washers and without.

Hi Marco,

if the spring pan goes down by 1.4" then the spring base will lower by this amount and thus so will the top.

The spring compression remain the same but the spring is displaced lower.

 

Roger

Share this post


Link to post
Share on other sites

Hi Roger,

in my imagination I set the TR on jacks under the spring pan, each hold about 250 kg.

And than I put washers between the pan and  wishbones. What moves up / down.

Isn't the spring base and lengh still the same and the wishbones with the trunions and wheels move up.

Sorry me if I'm wrong with this.

I better be quiet now.

Edited by Z320

Share this post


Link to post
Share on other sites
15 minutes ago, Z320 said:

Hi Roger,
in my imagination I set the TR on jacks under the spring pan, each hold about 250 kg.
And than I put washers between the pan and  wishbones. What moves up / down.
Isn't the spring base and lengh still the same and the wishbones with the trunions
and wheels move up.
Sorry me if I'm wrong with this.
I better be quiet now.

That was pretty much my thinking, but I didn't like to say anything
in case I was wrong.

The fulcrum pins are in a fixed position relative to the chassis
and the vertical link doesn't change length, so all you can do is
fit stronger springs (or pack out the existing ones) leading to
higher spring compression and a higher front end, or fit springs
with a lower rate leading to a lower front end.

AlanR
 

Edited by TR 2100
Typo

Share this post


Link to post
Share on other sites

Ha Ha !!!!

of course you are right (Marco and Alan)

by fitting the spacer between the wishbones and the spring pan you simply take a little load off the spring, the pan goes down  but the body stays put.

 

I wonder if some Twerp ever tried to correct Einstein. 

 

Roger

 

Share this post


Link to post
Share on other sites

Could it be possible the load on the  coil spring with the car on its wheels is the weight of the car?

Share this post


Link to post
Share on other sites

The height of the car front end is dependent on the length and rating
of the spring.

Long time ago (1985), you could only get the longer style front spring,
which meant that for TR2s, 3s and early 4s, you had to do away with
the aluminium spacer.

I didn't want that, so I had two springs of the corect (i.e. original) length
to suit the aluminium spacer.
QC was an issue even then, and one spring was obviously a lower rating
than the other, and the car did not sit level on the road.

AlanR

Share this post


Link to post
Share on other sites

I think we are making too much theory about this....

I will report back with my results....

Jochem

Share this post


Link to post
Share on other sites
6 hours ago, TR 2100 said:

That was pretty much my thinking, but I didn't like to say anything
in case I was wrong.

The fulcrum pins are in a fixed position relative to the chassis
and the vertical link doesn't change length, so all you can do is
fit stronger springs (or pack out the existing ones) leading to
higher spring compression and a higher front end, or fit springs
with a lower rate leading to a lower front end.

AlanR
 

Perhaps you should have bought SAH606 front springs they were the exact copy of the factory uprated spring as specified in the TR2-3 service manual.  Maintains the ride height but is a bit stronger.  Their latest reincarnation (TT4006) are a touch taller than factory originals when fitted Good for clearing road humps with your front anti roll bar.

Peter W

Share this post


Link to post
Share on other sites

Pete,

AFAIR  there were no "short" springs available at the time.
This was 1987.

Not sure I would have gone for stronger springs anyway.

AlanR

Share this post


Link to post
Share on other sites
5 hours ago, TR 2100 said:

Pete,

AFAIR  there were no "short" springs available at the time.
This was 1987.

Not sure I would have gone for stronger springs anyway.

AlanR

I agree Alan in 1987 the only standard height when fitted and  standard rating available were the 210903 late TR4 Spring that does not use the aluminium packing.   I sold many dozens of them to TR 2-4 owners.

Cheers

Peter W

Share this post


Link to post
Share on other sites

I am not sure how these comments adress my initial question, and just to put a damper on all theoretical approaches...

1. Lowering the pan has a similar effect as adding thicker/thinner shims. The front goes up, or the front goes down. This is common practice to have your car in similar height all accross the four fenders. The spring length is extended or reduced. In matter of putting spacers between the pan and wishbone the spring length is reduced, thus lowering the front. 

2. The pan is not flush to the wishbone. Putting washers or spacers in between does not change any of the forces induced.

3. Compressing a spring shorter is also a possibility....I have compressed springs on my shelf....unfortunately they are compressed 15mm...which would give about 30mm on the fender...which is too much....I am looking for something in between.

4. last but not least....where do I get longer studs? As John pointed out, the studs can have another 5-6mm....maybe it is enough....I will try it anyways.

Jochem

Share this post


Link to post
Share on other sites
30 minutes ago, JochemsTR said:

4. last but not least....where do I get longer studs? As John pointed out, the studs can have another 5-6mm....maybe it is enough....I will try it anyways.

just found them...

Share this post


Link to post
Share on other sites

I confess to being puzzled by some of the above discussion.

The lower wishbone is a fixed distance from the road surface, set by the radius of the wheel and tyre. The spring  - of whatever length  - supports the front of the car above the wishbone. Hence lowering the base of the spring relative to the wishbone will also lower the front of the car at that point by the same amount. The spring will remain compressed to the same length.

I don't understand Jochem's point 3 - there isn't much distance between the supporting point at the springs and the front of the car (assuming that  'fender' means bumper) so where does this 2:1 ratio come from at the bumper? The pivot point is at the back wheel so at most the extra movement will be about 1.2 times i.e. the 15mm at the spring becomes 18mm at the front bumper.   What am I missing?

 

Share this post


Link to post
Share on other sites

Fender=wing?

 

Share this post


Link to post
Share on other sites

The 2:1 ratio is due to the "leavers".

The sping on the spring pan is on the short leaver, the wheel on the end of the axle is on the long leaver.

I checked this with my spring compression tool (see eBay), thread bar M12x1.75.

For example 2 turns on the tool compresses the spring 3.50 mm, checked on the wheel arch 7 mm.

This is TR4A-TR6, I've been told on TR2-4 the ratio is less, I don't know.

Ciao, Marco

 

Edited by Z320

Share this post


Link to post
Share on other sites

Yes got that now thanks Marco, but I don't think the lever length of the wishbone does it. I see now that the lower wishbone inner pivot moves down with the body and so magnifies the actual movement by lowering the wishbone by about the same amount (though the geometry is complicated as the wishbone moves through an angle since the outer pivot is fixed).

Edited by RobH

Share this post


Link to post
Share on other sites

Hi Rob,

with another look on the construction I see this:

the wishbones rotate up and the wheel on the end of the leaver lift up "more", possibly double.

Jochem will find out and will share this knowledge with us.

Ciao, Marco

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.