Best gearing for speed

acotrel · Jul 3, 2019

I stay away from large race circuits. With a Commando engine, it is not 'IF' but 'WHEN'.

Champy72 · Jul 3, 2019

Somewhat negative?? My 850 has done well from last year into this, and on a standard 4 speed box!!
Hopefully it will continue until refresh this winter.

o0norton0o · Jul 3, 2019

champy, You can get a rear wheel sprocket that can be removed without removing the wheel or chain. They are called saw cut sprockets. You can also get them with a locking link version which helps keep them fixed for higher torque applications. The saw cut design is simple. The sprocket is made in 2 halves, so you can unbolt each half and it drops right off the wheel when you spin that half forward. You can install a different sized "saw cut" sprocket in it's place in minutes and change your final drive ratio without much disassembly. The only other thing you do is readjust the chain slack for the new sprocket.

I have a custom rear wheel application, so I needed a custom made sprocket to get the final drive ratio I wanted. I didn't buy the saw cut version for my bike because it's a road bike and I didn't feel I was going to change ratios like a racer might want to do. If you buy 3 saw cut sprockets all 1 tooth apart in size, you'll have extreme adjustability of power delivery given your 6 speed box.

https://sprocketspecialists.com/

They used to have pictures of their specialized sprockets on their website so you can see the saw cut version and the saw cut link lock version, but my guess is they don't feel the need to show the chinese that design to copy. I'm sure you can email them and they will send you pictures of their designs.

Champy72 · Jul 3, 2019

Thanks buddy!! That is great information. I'll give them a try...

SteveA · Jul 4, 2019

Champy72 said:
Actually prefer Gedinne - a much better road circuit with some interesting natural bends!
Can't get there this year, but definitely will for 2020 - visa's, carnets and certification dependant...

I love Gedinne, the avatar image was taken there (2017 and 2018).....but the lady of the house noted that she didn't want to spend her birthday and our 45th wedding anniversary in a field in Belgium!

Says it will be fine in 2020, see you there.

Champy72 · Jul 4, 2019

Ha! I'm lucky in having a bike/race mad partner, whose birthday is in March, mine in June and meeting anniversary in early August!!!
Not that a race weekend would be cancelled for any other reason than death!
Look forward to meeting up with you!

Champy72 · Jul 4, 2019

o0norton0o said:
champy, You can get a rear wheel sprocket that can be removed without removing the wheel or chain. They are called saw cut sprockets. You can also get them with a locking link version which helps keep them fixed for higher torque applications. The saw cut design is simple. The sprocket is made in 2 halves, so you can unbolt each half and it drops right off the wheel when you spin that half forward. You can install a different sized "saw cut" sprocket in it's place in minutes and change your final drive ratio without much disassembly. The only other thing you do is readjust the chain slack for the new sprocket.

I have a custom rear wheel application, so I needed a custom made sprocket to get the final drive ratio I wanted. I didn't buy the saw cut version for my bike because it's a road bike and I didn't feel I was going to change ratios like a racer might want to do. If you buy 3 saw cut sprockets all 1 tooth apart in size, you'll have extreme adjustability of power delivery given your 6 speed box.

https://sprocketspecialists.com/

They used to have pictures of their specialized sprockets on their website so you can see the saw cut version and the saw cut link lock version, but my guess is they don't feel the need to show the chinese that design to copy. I'm sure you can email them and they will send you pictures of their designs.

Seem to be only in US, and prices without shipping are high - $120 each. In UK, it would appear that you can only get karting split sprockets which are standard sizes and would not fit on the wheel!
Ah well, back to the spanners (wrenches) to get the wheel out if needs be...!

Fanfan26 · Jul 4, 2019

storm42 said:
Ha, it was the circuit impeding my performance, couldn't get going.

Are you doing Chimay and have you got an entry, I cannot seem to find how to enter.

https://circuit.be/Classic-Bikes-2019

o0norton0o · Jul 4, 2019

Champy72 said:
Seem to be only in US, and prices without shipping are high - $120 each. In UK, it would appear that you can only get karting split sprockets which are standard sizes and would not fit on the wheel!
Ah well, back to the spanners (wrenches) to get the wheel out if needs be...!

that's too bad, because the saw cut sprockets are for quick change applications, and racing really demands you experiment with different ratio's in a limited amount of practice time.

acotrel · Jul 4, 2019

The only way to set a bike up for racing, is to get on the circuit on your own with a lot of time and get perfect by making adjustments. If a race circuit is very different and a long way from home, it might be better race somewhere closer. Otherwise you are working on speculation, unless you get information from somebody who has already been there with a similar bike. And even then it is all subjective. In recent years, I have only raced at Winton and Mount Gambier which are both short fairly tight circuits. If I wanted to race the Seeley 850 at Phillip Island, I would have to do a major rethink and probably go there just for a bit of fun, with no expectation of doing any good. What you have to remember is that when it is bad, it is bad for everybody, but the local guys usually have an advantage.

acotrel · Jul 4, 2019

I don't like the thought of a split rear sprocket coming apart while racing. I'd be very careful about which types of bolts would be holding it on - don't use plated high tensile. It might be like fitting cast iron discs onto the front of an RG500 Suzuki, then finding out the theory had defects when you are braking at 130 MPH.

Champy72 · Jul 4, 2019

I think if I was starting out with no experience, your suggestion is right. However, I have raced sidecars and solos on most tracks in UK and Belgium, so what I am doing now is fine tuning. I'm afraid that the 850 is in the same class as the Imp 998, 1040 1200 engines, and BMW 850 and 1000, short strokes as well. It really is not competitive in the class I have been placed, but I do have a lot of fun with the 750's! Also, the classes in Belgium are more tuned to the 850, so I don't race with the 'big boys'!
At the end of the day, as long as I have fun and enjoy some close racing with any class, I'm a happy bunny!

acotrel · Jul 6, 2019

It does not really natter where you are in any road race, there is usually somebody there who will have a good go at you. Defeating them is almost as good as winning races, especially if they are riding a similar bike. And if you get done, you learn from the experience. So next time is different. If someone is faster than me, I always take note of where they are quicker and try to figure out the reason. If it is extreme top end power on a big circuit, you cannot do much about that with a Commando.

Champy72 · Jul 7, 2019

Well said.
If you follow a fellow competitor instead go trying to stay in front all the race, you find where they take a bend wide, or cut in too early, or don't use the right gear at a certain point.
That is when you strike, and the fun begins!

acotrel · Jul 8, 2019

Sometimes it is nice to let them see your front wheel come up beside them a few times, then do it to them big-time. One thing I found - with A -grade riders, they can help you lose a race in the pits by psyching you with their bullshit. If you get to be really good, don't do that stuff. Just them being there is enough worry.

acotrel · Jul 8, 2019

From what you have said, you clearly know what you are doing. I have never road-raced sidecars because I don't like having somebody else's life in my hands. However what you are doing is good. In about 1962, Orrie Salter - one of our Australian international riders returned with a 500cc Rennsport BMW. He ran it in the open sidecar class against Frank Sinclair's 1000cc methanol-fuelled Vincent and soundly beat him and all of the others. That sidecar ended up in the hands of Stan Bayliss from NSW. When Stan died, the bike went to Queensland where some idiot was trying to rebuild it as a solo. In Australia, many of us have no real sense of values. Orrie's sidecar was supposed to be returned to the BMW factory. But Orrie was a bit dodgey. Stan's som Steve must know where the Rennsport is now.

Champy72 · Jul 8, 2019

Not sure that I know what I'm doing! Well, not all the time ...
Everyone says that whoever passengers the sidecars must be mad, and to a degree they are right! Classic sidecar racing is nothing like F1 or F2 regarding speed or passenger movement, but interestingly there are more female passengers in the clubs than male!
Not heard of any serious or fatal injuries on these machines, unlike on solos, sadly. We lost a very popular lady racer who high sided and landed badly at Brands Hatch 2 years ago. The Air Ambulance has been called for solo accidents, but unheard of for sidecars.

storm42 · Jul 9, 2019

Fanfan26 said:
https://circuit.be/Classic-Bikes-2019

Thanks, that has got me to the regs, would you know if I need a medical certificate if I apply for a day licence at the track?

Thanks Ralph.

Champy72 · Jul 9, 2019

I know the ACU require a medical when you are 70, but I doubt if you even need to take your ACU licence, although I do, just in case.
Basically, you fill in the form, pays your money and that's about it.

acotrel · Jul 9, 2019

My brother races speedway sidecars and usually wins every race he enters. We have only ever lost one passenger. The bike had no stops on it's steering and snapped onto full lock. It bounced the passenger off the fence. These days, the rider can tell you almost to the minute how long ago it was that his passenger was killed. The guy now has a serious problem with alcohol. When I race I am only responsible for my own life. The kid who was killed was a lovely young bloke, he would have been his mother's pride and joy. I would never want that sort of worry. I have ridden sidecars on speedway and in scrambles, both as rider and passenger. It is good fun, but you need to take a lot more care. With a solo, it does not matter too much if you chuck it down.

Best gearing for speed

Similar threads