Suspension travel limit - which bikes?

[Rossvickicampbell]

Gents - which bikes are affected by the suspension travel limiting rules - both pre and post 75.  I know the YZ Bs in pre 75 have to be limited - what bikes after that and which eras please?

thanks

Rossco

[albrid-3]

YZ B, where on sale here in Australia, easter  1974, I think the rule to limit them is just crazy, I never agreed to it in the first place.

[sleepy]

In pre 75 the 74 Maico's where the first production MX bike with forward mounted shocks and they had about 6.5" travel. Also the the YZB as you mentioned had a similar amount. These bikes where forgotten about when the pre75 class was thought about as it was meant to be for bikes built before the long travel revolution. The 4" travel in the rear is a bit silly because almost all the bikes in the era had close to 5" at the wheel and 4" travel shocks. So all bikes built around 73-74 have to be limited to meet the rule as written.
Not sure about the ones in pre 78 but there are a couple that exceed the 9/9 inch rule.

[Nathan S]

This was asked a while back. If my memory serves me correctly...

The following 1977 models were factory specced with more than 9" of travel at either end:
1. RM125B;
2. YZ250D;
3. YZ400D;
4. Montesa (all MX);
5. KTM (all MX);
6. Husqvarna (all MX);

Can't recall for SWM, Bultaco or Ossa, and I have a vague memory that one of the Euro brands' enduro bikes were over 9" too.

[LWC82PE]

The thing is , how is travel really measured? Suzuki typically do not offer the claimed travel in the brochures unless compression/partial compression? of the rebound spring on top out is taken into account. I measured some stock 77 RM250 forks to have 213mm (8.38”) and the specs say it should be 220mm (8.66”) I could not physically compress the rebound spring by extending the forks by hand. I have found this to be the case with several other Suzuki forks too. So if your bike was checked at the races how would they do it? I cant imagine having to pull apart your forks measuring rebound spring and saying ok we think that would compress X amount and then add that onto the measured travel. So what I am saying is that there could be some bikes that have above 9” in the specs but when measured by just collapsing the forks they pass as having under 9” of travel and only actually measure above 9” if the rebound spring compression is inc. So what is a fair and consistant way of determining the travel?

[KTM47]

The thing is , how is travel really measured? Suzuki typically do not offer the claimed travel in the brochures unless compression/partial compression? of the rebound spring on top out is taken into account. I measured some stock 77 RM250 forks to have 213mm (8.38”) and the specs say it should be 220mm (8.66”) I could not physically compress the rebound spring by extending the forks by hand. I have found this to be the case with several other Suzuki forks too. So if your bike was checked at the races how would they do it? I cant imagine having to pull apart your forks measuring rebound spring and saying ok we think that would compress X amount and then add that onto the measured travel. So what I am saying is that there could be some bikes that have above 9” in the specs but when measured by just collapsing the forks they pass as having under 9” of travel and only actually measure above 9” if the rebound spring compression is inc. So what is a fair and consistant way of determining the travel?

I was the MA measurer at the Classic MX Champs at QMP in 2012.

Forks:-  It was just a matter of removing the fork springs and measuring the travel from compressed to extended, with a ruler or tape measure.  I didn't try to compress the top out spring etc.  I allowed a 5% tolerance because of the method of measurement etc.  So 9" is 228.6 mm add 5% it is 240 mm.  If you are over that you are well over.  Aim for 229 mm.  Also we are measuring the travel of the forks not the vertical movement.

Rear end:-  Again shock springs off and can be just the one shock left on.  Put bike on stand, take any sag out also, measure from centre of the axel to a point vertically (90 degs) up to somewhere on the frame.  Take the bike off the stand and compress shock to bump rubber.  No need to try and compress bump rubber etc.  Measure from axel centre again to same point on the frame.  The difference is the travel.  Also note the position of the chain adjustment can influence the travel slightly.  Aim to be slightly under the 229 mm that way there is no surprises.

I'm sure someone will try to tell me I did it wrong.  They are more than welcome to apply for an MA measurer's licence and do it next time.

[Slakewell]

This was asked a while back. If my memory serves me correctly...

The following 1977 models were factory specced with more than 9" of travel at either end:
1. RM125B;
2. YZ250D;
3. YZ400D;
4. Montesa (all MX);
5. KTM (all MX);
6. Husqvarna (all MX);

The Maico is too long as well.
More bikes than not, need to reversed engineered to comply. Its one of those rules that allot thought did not go into. IMO they should just have no rule for suspension travel in pre 78 the same as evo.

Can't recall for SWM, Bultaco or Ossa, and I have a vague memory that one of the Euro brands' enduro bikes were over 9" too.

[Nathan S]

Kevin, your method is perfectly reasonable and logically sound - but is legally indefensible if someone wanted to push the point. Not because you're method is wrong or unfair, but because you've been forced to invent a method that is not in the rule book.

Properly written rules are the real solution.

[Rossvickicampbell]

thanks - and does anyone know where the logic behind limiting the bikes mentioned has come from?  If I can remember rightly, and that is doubtful, there was an MA comment re everyone wanting to buy the bikes with the most travel and the other makes being "left behind" as a result?  I challenge this logic as for the YZBs there were only 1200 or so 360's made with probably 20 in Aus at best so everyone is not going to jump on that band wagon.

I am thinking about putting in a request to the MA commission to remove the limit rule but wanted to know what bikes were effected and what the logic behind the rule was?

cheers

[GMC]

Oh Christ, here we go again, just what the forum needs, another rule rehash!

Pre 75 was originally put together for the old school short travel bikes.
The intent was to celebrate the Era of short travel bikes, not just the year.
It was defined as Pre 75 without thorough research and it was then realized that some Pre 75 models had more than 4” travel.
At first there was some attempt to ban these bikes as they were the odd ones out with the short travel bikes but after much debate they were allowed in with restricted travel (which seems like a sensible option)
Decades later we now have guys crying foul that they have to modify the travel of their bikes to fit in with all the other short travel bikes.

Vision of the future;
Long travel bikes are allowed into Pre 75.
Long travel Maico’s are now sought after as 6” rear suspension is far superior than 4”
Fast guys will win on anything.
All the fast guys choose the long travel Maico’s so they can beat the other fast guy.
Maico’s are now hard to find.
GMC buys a welding robot and starts spitting out replica Maico frames
People fit other engines into the replica Maico frames.
The start lines are full of Maico framed Suzuki’s and Honda’s and Bultaco’s and Yamaha’s
Then some bright spark wants to fix the Maico framed bias of the start grids and allow modified laid down shocks on all Pre 75 bikes.
People start parking their bikes rather than butcher them to try and compete
The Era of short travel bikes is now lost forever[/i]

[211]

I guess a quick Email to [email protected] could be the solution

thanks - and does anyone know where the logic behind limiting the bikes mentioned has come from?  If I can remember rightly, and that is doubtful, there was an MA comment re everyone wanting to buy the bikes with the most travel and the other makes being "left behind" as a result?  I challenge this logic as for the YZBs there were only 1200 or so 360's made with probably 20 in Aus at best so everyone is not going to jump on that band wagon.

I am thinking about putting in a request to the MA commission to remove the limit rule but wanted to know what bikes were effected and what the logic behind the rule was?

cheers

[Rossvickicampbell]

thanks Dave - appreciate that.

Geoff - can see you woke up on wrong side of the bed today?  It isn't just pre 75 but later eras as well?  And what is wrong with simply asking a question or finding out what the logic is?  Few new faces on the commission now so no harm in asking.  And bugga me - a guy even expresses a comment about thinking of doing something formally - which isn't that what we all preach on here - and somebody has to get all sarcastic and facetious about it?

Damned if you do - damned if you don't.  And don't dare ask a question on here apparently.

[GMC]

Sorry Rossco, guess I have been on here too long and seen the same questions too many times.
You can apply formally if you like and I didn’t see my post as being sarcastic, just factual as I do believe the vision would happen in the space of a few short years.

As for the later Era’s I believe the Pre 78 class was meant for the early long travel bikes.
I assume they went through the same thing of banning bikes which had more than 9” or letting them ride with restricted travel
There will always be debate on this one as it is certainly debatable.
Comes down to the same question, do we celebrate an Era or do we celebrate a particular year?

Thing is, the guys that complain about the pre 78 travel are the ones that would only buy a 77 model to have the technological upper hand which is why I believe my pre 75 vision would happen.

(steps back now to avoid all the flack)

[Nathan S]

Our Pre-78 class was apparently a direct copy of an American class. That class has since changed to recognise and allow the 77 models with more than 9" of travel, but we have not followed suite.

Pre-75 was always about the short travel era, who's death began with the YZ-B and 1974.5 Maico. So while those bikes (and the 1974 KTM motocrossers) ARE legitimately Pre-1975 models, the class was always intended to exclude them (hence the travel limits).
I have no problem with this.
However, to exclude these bikes from racing in standard form in Pre-78 is absolute idiocy.

Pre-78 is less clear cut. The rules appear to be written on the assumption that no Pre-78 bikes had more than 9" of travel - and 9.5" or 10" is still clearly short of the 12" that became the norm in the Evo era.
Once again, the rules are not clear - and once again our peak body (the MA CMX/CDT Commission) is not providing leadership on the issue.

[KTM47]

Kevin, your method is perfectly reasonable and logically sound - but is legally indefensible if someone wanted to push the point. Not because you're method is wrong or unfair, but because you've been forced to invent a method that is not in the rule book.

Properly written rules are the real solution.

Ok smart arse. How do I measure the travel accurately without having a tolerance. The engine capacity for Classic racing has a 5% tolerance, that is where I got it from. The one bike that was excluded in 2012, was about 25mm over the 229 mm limit. Top out spring has no real bearing on usable suspension.

Pre 75 has had the current limits for years now, while I personally don't like it I wouldn't try to change it. As for Pre 78 I personally think 10" (254 mm) would be better. Anyway if you want to change it read the MOMS. It can't be changed until next years commission meeting. March 2016. Posting about it here is not going to change it.