motocross a-arms setup

[rablack21]

I had a guy that sold a-arms tell me that +2+0 a-arms were the best setup for motocross and that +2+1 a-arms were more used for TT, and that 250r frames had some binding issues with using the +2+1 arms. Is there any truth to that?

[250Renvy]

My understanding of the setups come from talking to someone who actually developed them.

He told me that almost all aftermarket a-arms are +2+1 for the 86 and just +2 for the 88/89. I'm not 100% sure on 87.

The reason is that stock 88 a-arms if they could fit perfectly on a 86 frame would be +1 forward. Since there were so many 86's out there the a-arms were made for the better 88 geometry of +1 forward, but if you put those same a-arms on an 88 they would be just +2. So depending on what frame you have, the a-arms would be +2+1 or just +2+0.

Otherwise +2+1 from the standard 88 position would be +2+2 from the 86 position and I'm not sure I've heard anybody mention that.

So to answer the question about MX vs TT. I'm not sure one is better for one than the other, but binding might be an issue for TT because of the stance, but I've never heard anybody having issues. It may depend on what a-arm they are running.

[deathman53]

the real issue with a-arms is the individual types and brands. Adjustable camber and caster play a big part. I have a roll lobo +3+1 and laeger +3+1 t-pin. they turn and handle so differently. One is on a stock frame and other is on lsr hybrid. T-pin being better for woods and tight mx, roll lobo better for hi-speed. I have a lsr +3+1 also, it could be changed around by changing the caster(spindle front-back). Being forward(+) on it, it turns really fast and back, it starts to turn slower and hi speed stability.

[trx310R#24]

mine is +3+1 and i love it

[86 Quad R]

Originally posted by trx310R#24
mine is +3+1 and i love it

sooooo no binding issues? :cool:

[fourtrax_r]

found thi on the other 250r site. some info in here may be helpful to the original question

The TRX250R was introduced for the 1986 model year to answer Suzuki’s LT250R, released the year prior. Honda borrowed many parts from its 3 wheel ATC250R for the Fourtrax’s design, including the engine and rear suspension. Although mechanically similar, Honda detuned the engine for use in the Fourtrax, through reduced compression and less aggressive porting, to ensure that the added weight of the quad would not adversely affect the reliability of the engine.

The 1987 model year, now absent the three-wheelers due to the CPSC ban, saw the engine receive a five-millimeter longer connecting rod, accompanied by a piston with a wrist pin bore raised five millimeters. Additionally, the cylinder was changed to include a bridged intake. Most of the chassis of the 1987 Foutrax remained the same.

The 1988 model year brought the most dramatic changes to the TRX250R. The compression ratio of the engine was raised to generate more power, bringing it nearly on par with Kawasaki’s powervalved Tecate-4. It was the chassis, however, that received the greatest attention, shedding 25 pounds over the previous year’s model. Additionally a shorter aluminum swing arm was added, but the frame lengthened such that the overall wheelbase was slightly greater. This shifted the weight bias rearward, curing the Fourtrax’s “loop out” problem. Aesthetically, the Fourtrax’s headlight was moved from the handlebars to a mount molded into the hood. This was also the only year to be available with red fenders.

For 1989 the TRX250R received few changes. Most notable was the use of a needle bearing in the clutch pressure plate, for smoother action. This needle bearing was a necessary upgrade for the 1988 TRX250R, as well [3]. The color was returned to white for its final year.

[rablack21]

Great information fourtrax_r! However, let's just get down to the nitty gritty. Has anybody ever had any binding issues with any +3+1 or +2+1 arms on stock frames? Is so, what was the setup and what year model frame? I am specifically curious about the 86 model frame, but post any issues you have had with any year.