Bushings

[kozak]

Does any one use or have experience using hard plastic bushings (delrin) on the inboard of a-arms. i was looking on the site for what size and type of rod ends teams use on the inboard of a-arms then i came across a pic of a team that used bushings on the inboard.

[kozak]

Does any one use or have experience using hard plastic bushings (delrin) on the inboard of a-arms. i was looking on the site for what size and type of rod ends teams use on the inboard of a-arms then i came across a pic of a team that used bushings on the inboard.

[jack]

i would be afraid of ovalizing them, and then becoming sloppy.

then again, i have never tried it. our baja team is trying it this year, we will see how it goes...

[kozak]

we have used them on our baja car for several years. i don;t know if they see the same forces but i know they do get the crap kicked out of them.

[welder]

IIRC the Radical clubsport(?) uses plastic bushes inboard.

[jsmooz]

We've used Nylatron GSM (molybendenum impregnated nylon) without much issue. It's pretty stiff. Our baja team has used it for years without much slop being created even with all the pounding they see. You can always ream out the center and put a steel sleeve in it to resist ovalization.

[PPAM20]

I have run delrin bushings in racecars and roadcars. In my opinion they are a really practical approach. Inexpensive and Very durable - Couple of points. 1) Nylon is generally out - not good when it comes to impact loads. If you do use nylon ( they are very cheap), use very thin cross sections. 2) As the previous message suggested - definitly run a steel bushing inside the delrin bushing - the bolt must clamp against the steel sleeve, not against the plastic bushing. 3) In an A arm, the axis of the 2 inner mounts must be concentric. The plastic bushing does not allow for misalignment like a rod end or spherical joint would. An a-arm designed for plastic bushings must be designed so the bushings remain concentric after the manufacturing process. 4) 2 and 3 means you will not get points in the weight department, but the bushings are definitely cheaper and in many cases, do the job as well or better than a rod end.

[PPAM20]

PS - The nylon I was speaking of in the above message is nylon 6/6 or 6/12 - not the reinforcednylons or nylatron gsm previously mentioned

[kozak]

ok but if you use the bushing in the bushing then it will be metal on metal contact. we use oil impregnated delrin because it is self lubricating and we don;t have to grease it.

[jack]

is there a way to do anti dive/squat with bushings? i guess you could weld them onto the frame at slight angles but that would be very hard to do. you certainly cant have adjustable anti.

i forgot our car had bushings inboard in 04', and the fact that it has no anti causes some problems with setup and scraping. i spec'ed the new car with rod ends inboard mostly so we could play with anti and see what it does for us.

you guys know more about it then me though, and i guess our baja team just welds the whole front of thier frame at an angle (they run posi-dive though).

[Brian Evans]

When I make plastic bushings I use a teflon impregnated material formulated for low stiction, and I use a Thomson linear bearing shaft to make up the sleeves. The Thomson shaft is very hard and ground on the outside, but is soft on the inside so it can be drilled easily. I ream the bushings after assembly so that I can use a large interference fit in the A-arm. Alignment is critical - if the tabs on the frame or the fabrication of the A-arm impart any twist to the bushings relative to each other the whole affair gets very stiff.

I've run them for multiple years on roadrace cars (sportsracers, etc), and I've never had one even start to look like wearing out.

Brian

[jsmooz]

kozak - it doesn't have to be metal-metal contact. If you make the steel insert smaller than the width of the bushing then it won't rub your mounting tabs. Also, if memory serves me correct, the Nyatron GSM is self lubricating too.

jack - unless your bushings are threaded into the A-arm (like a rod end) then you couldn't adjust anti-. I don't know why you'd want to thread bushings like a rod end because you then lose the cost savings of going to the bushings.

[kozak]

as far as metal to metal i was thinking more metal bushing to metal bolt because the bolt rides in the middle of the bushing. and if you use metal bushings on the inside doesn;t that defeat the whole purpose of using impregnated plastic? right?

[jsmooz]

That metal to metal contact is very minimal, depending on how you look at it. Most of the friction comes from the ends of the bushing contacting the mounting tab on the frame. Think about it this way, the bolt has to slide through the steel insert. When you assemble the suspension the bolt is meerly pinching the ends of the bushing to the frame tabs. There is very little contact between the bolt and bushing/insert (remember it has to slide..ie clearance).

I think the friction is why many people shy away from bushings. However, I think rod ends have more compliance issues over time than a properly made bushing that makes up for the friction. Once you break things in it's pretty smooth too (bushings).