XRAY - Model racing cars

hi, can i please get some help becuase i have the best car at the track, my xray, but i come last because of handling issues.

my car is near new so nothing is worn completely stock with a mamba and 5 cells. hitec 81mg and airtronics rx\tx.

it corners very well but cannot drive a straight line. even at low speed the back seems to wobble side to side throwing off any attept to hold it under throtle. it seems to veer as well and either tracks left or right as if servo wasnt centering but i know the servo is plenty strong enough to center.
please help

chris

Which Servo are you using? When you say wobble do you mean like it dog tracks or do you mean the steering wont center?

its not the steering it doesnt budge. the rear end wobbles creating instability. is it perhaps the two rear wheels have different te in and are fighting each other?

(realizes you stated the servo) Opps!

Hmm.. When you lift the rear and hit the throttle, do the rear wheels make the car shake in your hand?

Wobble makes it sound like one part of the tire is heavier than the other.

-Is your toe in on the rear even? You mention this, have you measured though?
-Are your rear hubs on straight and in the "D" connection on the universal
-Do your tires themselves wobble back and forth looking from top down.
-Taking off the wheels and shocks, do the suspension arms drop under their own weight?
-How are your droop screws set in the front/rear (even)?
-Disconnect your universals from the differential. Spin the tires this way and see if both spin freely.
-Do you have the same offset on the rims with your rear tires on both sides, and are you using the rear tires on the back?

Thats all I can think of now. Let us know.

it seems to have two problems, related im not sure.
if i drive forwards slowly or fast with no steering input,
it will track straight for about 3-4 meters then veer right and turn in a long arc. at high speeds this is devestating on the fast long straights. i dont think its glitching because the servo is silent and solid.

im stumped.

The 81mg do have a recentering issue that can occur with the output spline. It may indeed seem silent and strong, but it doesnt mean the output spline is. If you have the Xray servo saver (get one if you already haven't), you can use the 81s plastic gear set as it can absorb the shock better.

which servo would you reconmend being the best?
trying to find xray servo saver, no luck yet. xray parts are hard to track down. where do you buy online?

The MG is fine if again, you really make it a "S" with the top gear. A new 81s gear set should be relatively cheap.

Can you borrow someone elses servo just to verify before you go through all that trouble?

I cant tell you where to go online, as I don't even know where you are. What about your LHS I always try to support them first?

would the s gear set help re-centering issues?
i'm in australia and my lhs doesnt stock xray unfortunatly
i normaly use rcmart or rcboyz

well i know its not the servo as i replaced it with a new jr and it does the same thing. just a note the hitec was a better servo. much quicker and responsive. i think its somwhere in the chasis or suspension. everything seems tight though.

???

all these ideas are great but i dont think its it, because i would think any instability would need speed to show itself. but. even at a crawl, my car will sometimes track straight, next pass will veer to the right. the rear wobble needs some speed to show up, but the veering happens at any speed.
my problem is on the track when it veers down the straight when im hammering wot i try to correct and always end up fishtailing every lap. almost ready to give up. i have a m18t on the way, hope its better.

So I take it the servo didnt help?

Fishtailing? Thats sounds like more a setup problem. What is your track surface and what tires are you using? Can you take 1 or two pictures of your car?

track is highly polished dusty concrete ( old rollerskating ring) tires are foams- i tried rubber but foams slide with more consistency.
it fishtails because it wont drive straight and at high speed on a slipery suface fighting to stay straight involves weaving all over the track. funny thing is, around the corners its unreal. real stable as it drifts around. just the long staight i cant do.
ill take some pictures later if i can. not sure if it will help though. im racing tomorrow night, hope it goes better

Im not sure, and I dont want you to spend more money then you need. But it sounds like some Ball Diffs might be the key from your description of the surface? You need something that will allow the drivetrain to slip a little since that surface lacks so much traction.

What you might do if you have a m18t on the way, just to try one thing at a time. Is use its ball diffs in the m18 for a run just to see how the car reacts (after you break them in). If it doesn't make a difference, then its something else. If it does however, well then you know.

Also, are you allowed to sweep/wash the concrete first? Use traction compound? Have you tried other rubber compounds? Sometimes on dusty tracks, rubber can work better.

More than any other, have other people at your track drive it/watch it (especially if they own M18s). They might be able to help you figure out where the problem lies. We are kinda flying blind here.

Let us know your results either way.