TC Rod geometry question

[Bears510]

OK my Ratsun brothers, I have a question for you that I hope you can help with.

I know there are several version of TC rods available to eliminate the weaker rods our dimes came with as well as they free up the suspension by using something other than the stock or poly bushings for freer movement. Also it gives the option of adjustability for alignment purposes.

I would assume the TC rod changes the alignment of the suspension throughout the range of motion due to limited length as it moves and in that thinking, does that negatively effect the geometry of the suspension? or is it a positive effect aiding in something like toe in/out or whatever. Does this hinder cornering or help? I have read tons of posts on here about tc rods and the benefits of aftermarket but have never really seen anything stating wether it helps, or hurts suspension allignment throughout it's range of motion?

Any insight would be GREATLY appreciated!!!

THANKS!

[sssr20det510]

TC rods should affect caster

[INDY510]

If you tighten the stock T/C rods your car feels more stable at high speeds and it is harder to turn in parking lots.

If they are loose your car will "jump" all over the road,

 

 

I have broken a stock T/C rod with poly bushings,,, and luckily I didn't wreck anything (I've heard of people tweaking the whole strut tower because of a broken T/C rod)

 

 

Poly bushings = FAIL .......... rubber bushings = okay ............. $200 adjustable T/C rods = priceless

[Unclejesse88]

T/c rods are used to maintain caster, but caster changes inherently affect toe. That is why toe is adjusted last during an alignment. I would say that aftermarket t/c rods would affect caster and toe the same as the stock ones. The best mod would be had by copying Duke and moving the t/c mount up when you lower your car. This would place the t/c rod back towards level at ride height.

[thisismatt]

T/c rods are used to maintain caster, but caster changes inherently affect toe. That is why toe is adjusted last during an alignment. I would say that aftermarket t/c rods would affect caster and toe the same as the stock ones. The best mod would be had by copying Duke and moving the t/c mount up when you lower your car. This would place the t/c rod back towards level at ride height.

Except that most aftermarket t/c rods end up with a pivot farther back than the stock bushing, so the affective rod length is shorter than stock.

[Duke]

Matt is right. There was a discussion on the realm a while back about how shorter T/C rods affect suspension geometry. Apart from the obvious caster issue, a shorter T/C rod also has an affect on toe change throughout suspension travel. This is due to the smaller arc that the shorter T/C rod swings through. This has the affect of inducing toe out under a compression situation, such as hard breaking. This toe out can make the car very skittish under heavy breaking. The shorter T/C rods will also have an affect on bump steer because of the same reason.

 

However, one thing that must be taken into consideration is that with the amount of suspension travel most of our 510's have, there may not be enough movement for the change in toe to be noticeable.

[Bears510]

Matt is right. There was a discussion on the realm a while back about how shorter T/C rods affect suspension geometry. Apart from the obvious caster issue, a shorter T/C rod also has an affect on toe change throughout suspension travel. This is due to the smaller arc that the shorter T/C rod swings through. This has the affect of inducing toe out under a compression situation, such as hard breaking. This toe out can make the car very skittish under heavy breaking. The shorter T/C rods will also have an affect on bump steer because of the same reason.

 

However, one thing that must be taken into consideration is that with the amount of suspension travel most of our 510's have, there may not be enough movement for the change in toe to be noticeable.

 

I knew you guys would have the answer!!!

This is what I was tying to find out, if under braking and cornering there is any effect on the alignment wether good or bad. I guess I'm just curious if the tc rods were put in a certain position for a reason. kinda like how newer suspensions have "anti dive" built into the geometry.

So basicly, and PLEASE correct me if I am wrong, but tc rods are really just there to support the LCA's (keeping you on the road...lol!) and do effect castor with some adjusting which could be good or bad. other then that...no other real positive or negative effects by them to any major degree? again, other than keeping you on the road by supporting the LCA's?

 

I agree with you on your last part as most of the people on here have lowered or slammed 510's so there isn't going to be much travel to truly notice any differences in the change.

Thanks guys!!!

[datzenmike]

Without the TC rod the LCA is hanging out there in space. When the wheel drops into a pot hole or hits any obstruction even slowly, like climbing a roll curb to enter a driveway, there is significant rearward energy trying to force the wheel and LCA backwards and bend the transverse link where it mounts to the front crossmember. The TC rod forms the third arm of a stable triangle to support the LCA.

[Bleach]

weeeeeeeeeee!

 

[Bears510]

Without the TC rod the LCA is hanging out there in space. When the wheel drops into a pot hole or hits any obstruction even slowly, like climbing a roll curb to enter a driveway, there is significant rearward energy trying to force the wheel and LCA backwards and bend the transverse link where it mounts to the front crossmember. The TC rod forms the third arm of a stable triangle to support the LCA.

Exactly, if it wasn't there, the LCA would push back as far as the bushing would allow until the LCA bends/snaps or the bolt does...ACK! but is it's placement a benefit, hinderance or has no MAJOR effect on alignment or handling, other than minor castor adj? yes? no? kinda? lol! I think someone earlier said something about raising the pivot point if you are driving a lowered dime (probably a majority of us) does help with the angle so it's more level and not already in an upward arc. that makes total sense. I understand the main reason for the TC rod, just didn't know if there was any side benefit/downside to it's placement. probably just over analyzing it...lol!

again..THANKS for your help!

[zerow]

...The best mod would be had by copying Duke and moving the t/c mount up when you lower your car. This would place the t/c rod back towards level at ride height.

Can we get a pic of this condition? The 510, 610 and 710 effectively have the same front suspension, so I am definitely interested in this as I have taken a couple of inches off the front of my 610 sedan.

[datzenmike]

I don't see why the TC isn't modified and placed in the exact center line of the transverse link on it's own bushing. This would effectively lengthen the LCA base length making it a huge triangular door hinge that can only rotate around the transverse link center line and impossible to add any changes to camber or castor.

[Unclejesse88]

Can we get a pic of this condition? The 510, 610 and 710 effectively have the same front suspension, so I am definitely interested in this as I have taken a couple of inches off the front of my 610 sedan.

 

If you hunt down Duke's build thread there are pictures of him raising the t/c mounting points.

[thisismatt]

I don't see why the TC isn't modified and placed in the exact center line of the transverse link on it's own bushing. This would effectively lengthen the LCA base length making it a huge triangular door hinge that can only rotate around the transverse link center line and impossible to add any changes to camber or castor.

Even with the LCA and T/C pivoting on the same axis, the hub still has to move with relation to the strut. You're going to have camber changes throughout suspension travel no matter what position the LCA & T/C rods are in, no matter what, because the strut bottom has to swing in/out through travel as it's pivoting at its top mount and has to follow the arc of the LCA & T/C combo. The same is true for caster unless you have the geometry set up in such a way that the strut is perfectly centered between LCA & T/C so that there's no forward/back movement of the strut bottom through LCA & T/C arc, or the LCA & T/C arc move in such a way that they don't move the strut bottom forward/back.

 

That probably didn't make any sense.

[datzenmike]

:lol: I was afraid I wasn't making any sense.

[Duke]

Can we get a pic of this condition? The 510, 610 and 710 effectively have the same front suspension, so I am definitely interested in this as I have taken a couple of inches off the front of my 610 sedan.

 

Here you go...

 

 

The first picture shows how I moved the t/c mounting point up (1" if I remember correctly). I did this to match the amount that I moved the lca pivot up to help with roll center with how low my car is. The second picture shows my t/c and lca setup using a heim joint for the lca pivot and the inner tie rod end from a 280zx as the t/c rod pivot. Using the inner tie rod end for the t/c rod pivot keeps the t/c rod longer than if you use a heim joint. Also they were only $10 on rock auto as opposed to around $50 for good heim joints. The new Futofab setup uses a similar pivot.

[zerow]

Here you go...

 

 

The first picture shows how I moved the t/c mounting point up (1" if I remember correctly). I did this to match the amount that I moved the lca pivot up to help with roll center with how low my car is. The second picture shows my t/c and lca setup using a heim joint for the lca pivot and the inner tie rod end from a 280zx as the t/c rod pivot. Using the inner tie rod end for the t/c rod pivot keeps the t/c rod longer than if you use a heim joint. Also they were only $10 on rock auto as opposed to around $50 for good heim joints. The new Futofab setup uses a similar pivot.

 

Thank You for the pics!

[Bears510]

This was a lot of great info guys...THANKS!!!!