View Full Version : Chassis Tech & recommendation needed
We are currently running two 6 yr old Birel Q30's in Yamaha Jr. Supercan and Formula Y Jr. Lately, we are having trouble getting them to be competitive due to chassis handling. We do realize there may be some driver error involved too.
Does the kart chassis flex less as it gets older? Is it less responsive to adjustments? Also, is that why top national drivers get new chassis every couple months or races?
Our chassis have seen quite a bit wear and tear over the years. They have been bent and restraightened numerous times.
It has been said to us that Motorsport Birel chassis are made w/chrome moly tubing. The top Birel Teams are given select hand welded chassis's (To control heat better.). Base Birels are produced from a mild steel and
assembly line welded. For this reason it was suggeted tous to get rid of our Q30's.
We have been in karting for only 3+ years so the driver and crew chief still have much to learn. We seemed to have tried everything on set-up but are still missing the top racers by .5 - 1 second laptimes. Can anyone else running the Q30 Chassis with soft DBS tires offer advise? It drives like a truck; binds up and wears out the front tires quickly. I am thinking of buying new chassis's for next year to rule out if the chassis is the problem. What new & latest design Birel chassis would be recommended for the Jr. supercan and Formula Y Jr. classes?
09-15-2004, 12:42 AM
This is a really good question and I will have one of my more gifted writers respond to this posting. We have strong ideas. You are correct in your assumptions. When is a chassis worn out? When dramatic changes fail to produce positive or negative changes on the stop watch. More in a few hours.
09-15-2004, 10:05 AM
Your questions are good ones for sure, and need to be answered for everyone reading.
First of all, although not every line of Birel is hand welded, very few are done by robot. ALL of the chassis models used for racing are hand welded. Factory teams from Italy may select a particular frame to assemble, but here, all the best drivers take the kart from the box (the same as all customers receive) and put it on the track. There is no special kart for national level teams. There is no "special" steel used in national team karts. No special welding technique is used. Each kart is as close to being the same as the next as is humanly possible. That is why the birel kart works so well. They are all made equal.
All metal will fatigue with use and age. Once the frame has sagged, you will no longer be able to get the front end geometry back to where it needs to be for the kart to handle well. You can certainly extend the life of the frame by straightening it, but there comes a time when only "new" will solve your handling problems. Once the kart is sagged to its maximum, then you are correct in your assumption that it will no longer flex as it was designed to do. On the way to that "worn out" point, you will experience too much flex which may cause an over grip situation. When chassis adjustments fail to make much difference in the kart handling and performance, you have in all probability, reached the end of the useful life cycle.
If you are tearing up front tires, there is little doubt that your alignment characteristics are not where they need to be. Seat placement can also be a factor that might cause tire wear problems. However, your plan to consider purchasing new karts is right on target. There is little doubt that you will see a big improvement in driver lap times.
In terms of choosing the best suited chassis, driver size and weight will usually figure into the selection, but for the most part for the classes you are running, the R30 will be a very good choice.
I hope that you will find this information helpful in making your decision for your future kart racing needs. If we can be of more help, please do not hesitate to add to this thread, or contact us directly.
Bruce - MRP Motorsport
Thanks for clearing things up & the info. As far as tearing up front tires and handling problems, when I scale the kart I get 42 - 43% front weight and within 5-7 lbs left to right. Usually the same variance for the rear. If it gets over 15 lbs we usually find that the frame is bent. If I add weight to the front the tire wear & handling gets worse. The seat is positioned equal to the bottom of the frame. These factors all seem to be in the ballpark so that's why I questioned the chassis wearing out. The driver, my daughter is 5'2" and 100 lbs so the majority of the weight is bolted on the seat up high to help her flex the kart.
As far as the new chassis goes I heard the new R30 is not as fast as an older R30. I also saw an AR30. Does this chassis exist? Are you going to be at the Birel Expo and swap meet at South Bend in October?
09-18-2004, 06:44 AM
Weight distribution is good on your scaling, so the tire wear must be a result of camber / toe angles / kart condition, as seat placement (based on your info) can be ruled out of the problem. You may be able to correct some of the wear, but it is unlikely that the time spent will result in any better handling or laptime characteristics.
As a matter of interest, what are you using to check / change / measure alignment on your kart? There are a number of good tools available, with the laser being the most accurate and easy to use. I would be interested in knowing what your current camber and toe measurements are.
Interesting comment on the new R30CY. We have a number of customers running the new kart with fantastic results. Two of them in particular, moved to the R30 from a different birel chassis, and so did not have a bench mark for set up from the older version. It is my opinion (and experience) that drivers / tuners tend to take the new version of a kart, and duplicate their set up from the old version to make a comparison. In many instances, they are not happy with the comparison results. It is imperative that the new version be tested for what it is, a NEW VERSION. Just as you would not copy the set up from a different manufacturer, you should not expect the setup on a new kart to be the same as on an older version.
I have found the new R30 to be every bit as good or even better than the older version. It is simply a matter of getting used to the new kart and finding the best set up to make it work. Things change. Many people resist change. However, staying the same and hoping for better results simply does not work. We should never stop trying new setup combinations and strategies to get our very best results at the track.
My position is simple. The birel karts ALL work. It is up to us to find the best set up for each unique driver, just as we must find the best setup for each track and each changing set of track conditions. It is never exactly the same and I know that you have experienced this having raced for the time that you have.
On your last question, the answer is Yes. There is a model AR30. The difference is similar to the difference between an AR1 and an AR4. While the AR1 is narrower than the AR4, so it is with the AR30 being narrower than the R30. Typically, the narrower version kart will be better suited for a lighter driver weigth, lower horsepower engine and a tighter track layout. Both the AR30 and R30 have welded seat struts. Depending on your specific requirements, this may be a very good choice for your driver.
Finally, I do not have plans (at this time) to be at South Bend in October. It is quite a trip for me to get there, and the calendar is fairly full at this time. However, (as mentioned) things change! As we get closer to the event, perhaps the trip will find its way into my schedule.
Thanks for taking the time to post your questions to the MRP forum. I believe that this kind of information exchange is great.
Bruce - MRP Motorsport
Thanks for the feedback. Your info is very helpful. I use a Longacre bubble gauge to set camber. It only goes to 8 degrees castor, so I can't check that. I run 0 degrees camber. This gives me the best tire wear/contact patch. I don't have a tire pyronmeter to measure tire temps to verify this. My too-in/out is set by using an Exact-Toe gauge. I run 0 degree toe. All setting are done with the driver in the kart. I use the adjustable pills on the top to set camber, ignoring castor. Maybe this is part of the problem since castor may different from side to side. I have set it at full positive castor with the 1.5 pills but it didn't seem to help too much. I always thought camber was more important to handling than castor. Based on your feedback I think my chassis is just worn out. Is there a place I can go to get more info (dimensions/ options) on the R30 & AR30's? The MRP website has only pics of the R30.
Has anyone run the AR30 model in Jr. Supercan or Formula Y? What success did they have? Is the AR30 a newer model? I agree with your comment "All Birel karts work." It is finding which one works best with the driver and class. Just as, I have been advised to go with a Q31 in these classes. Even though all the top drivers are using it, my daughter is so light I feel she will have trouble flexing the chassis. Thus, I would not be able to dial it in to go fast and be competitive. The AR28 would be too flexible with the horsepower range of her engines. This is why I like the Q30. It seemed we were getting progressively faster until she wore them out.
I had assumed if you answered the MRP website you were located in the area. I look forward to meeting with you someday.
09-25-2004, 09:03 AM
Good Morning Ken
Sorry for the delay in response. Busy week here..........
I am surprised that, with the adjustments you have made to the front end alignment, you still have such agressive tire wear. I am not familiar with the Longacre bubble guage, and so cannot comment on its accuracy. The exact-toe guage is fairly accurate, and so I would guess you are good on toe. I agree that the camber angle is important to handling, while caster is used to grip the kart (more or less) as it influences mechanical jacking of the chassis while turning. You can use the exact-toe guage to measure camber by simply turning the attachments vertical (usually down) and running the bar side to side under the frame. I like this method as it better provides relational measurements of camber as opposed to individual wheel readings (which rely on the kart being level when taking measurements).
In any event, I do not think that we need to spend too much more time on assessing the old chassis, as we tend to agree that it has seen its best days some time ago.
I have not had personal experience with the AR30 Chassis, but can advise that extensive testing on this kart is underway. Once complete, I will be happy to pass on professional experience that will test the AR28 and AR30 in Junior 2 cycle applications. More on that later (as available).
The AR30 is not a newer kart than the R30, but is of the same vintage. I can provide specific dimensions on each and will be happy to do that in a direct response to you.
The testing that I refer to above will be in 2 cycle applications that will give you a good idea of the performance of the AR30 and will perhaps aid in selecting which kart will best serve your needs. The Q31 is an excellent kart but certainly is stiffer in the middle of the kart than either the R30 or AR30. Driver weight is a big consideration in selection of the "best" chassis(for your driver), and should be considered in your decision. Your final choice will come from the selection that includes AR28, AR30, R30, Q30 and Q31. We will do our best to narrow the selection as best we can based on more details from you.
Although I am not as close geographically to MRP as I would like to be, I am priviledged to be extremely close to the group in terms of information. Both Tim and Chris Lobaugh are among the very best chassis tuners available anywhere. I trust their opinions without question, and value their advice which I continue to consult with as often as possilbe.
Thank you for your continuing support of the MRP forum. As mentioned above, I will be in touch with you to more specifically answer some of your questions.
Bruce - MRP Motorsport.
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