spurs59 Posted May 31, 2012 Posted May 31, 2012 im led to beleive that by using a smaller back sprocket i will get more top end speed,how many teeth do i need to go down on from the standard sprocket
Moderator DirtyDT Posted May 31, 2012 Moderator Posted May 31, 2012 True. Big rear sprocket = better acceleration, lower top speed. Small rear sprocket = better top speed. lower acceleration. However; There is a price to pay because if you mess with the sprockets you affect the gearing so riding up hills or with a head wind will be more difficult. Only consider doing this is you ride mainly in top at near the top end of your bikes speed. With a DT I wouldn't change the gearing. If you do intend to, minus one tooth would be enough. There is a spreadsheet to calculate what the changes would be in Excel. You should be able to find it with a little googling - motorcycle gearing worksheet or LINKY for an online one.
spurs59 Posted May 31, 2012 Author Posted May 31, 2012 True. Big rear sprocket = better acceleration, lower top speed. Small rear sprocket = better top speed. lower acceleration. However; There is a price to pay because if you mess with the sprockets you affect the gearing so riding up hills or with a head wind will be more difficult. Only consider doing this is you ride mainly in top at near the top end of your bikes speed. With a DT I wouldn't change the gearing. If you do intend to, minus one tooth would be enough. There is a spreadsheet to calculate what the changes would be in Excel. You should be able to find it with a little googling - motorcycle gearing worksheet or LINKY for an online one. so you recommend i keep the standard sprockets?
Moderator DirtyDT Posted May 31, 2012 Moderator Posted May 31, 2012 The DTR is about fun and thrashing the gears. So personally I would keep the sprockets the same. There was a huge amount of cash thrown at getting the gearing right at the design stage. If It was a big 4 stroke thumper that you wanted a few more MPH out of then doing this would be OK (in my opinion). Other people may disagree with me. Standard is good.
flyday58 Posted June 3, 2012 Posted June 3, 2012 For me, getting to the fun places to ride is the most dangerous part of the journey. I live in the land of big ole trucks and trash mass-made American auto-mobiles, so I can never go fast enough for people. I've ridden the M4, M25, and Hammersmith flyover enough to know that you have a similar issue in the UK. I need the higher speed to stay (mostly) out of the way of the Top Gear set. Not too many Captain Slows over here. I went from 49 to 45 teeth on the rear and I now get 50 USmph at 5000 rpm, down from around 5500 before. As noted by DDT, she fades uphill due to the gearing and runs out of steam about 5800 rpm in 6th gear, but I'm good with it.
oldbikerehab Posted June 3, 2012 Posted June 3, 2012 I have two extra teeth (18) on my front sprocket and stock (49) on the rear and get about the same top speed/rpm specs gains as flyday58 on the same bike. Dirty's comments on a bike's original design and standard being good are spot on though. I'm about to switch back to the 16t/49t original spec. Mostly because I want to see what the bike is supposed to be able to do and tune from there. If you know how to really tune the bike and make adjustments to fuel, timing, air flow, exhaust, jets, etc. to compensate for the possible strain your initial change may make on the bike - go wild. Otherwise, go standard.
Moderator Airhead Posted June 3, 2012 Moderator Posted June 3, 2012 your bike is fast enough as standard, i got an indicated 80mph downhill on my DTR but at that speed its pretty hairy, not streamlined in any way whatsoever...for me a good healthy top speed and fast accelleration beat unstable engine screaming top speeds...hands down
flyday58 Posted June 4, 2012 Posted June 4, 2012 your bike is fast enough as standard, i got an indicated 80mph downhill on my DTR but at that speed its pretty hairy, not streamlined in any way whatsoever...for me a good healthy top speed and fast accelleration beat unstable engine screaming top speeds...hands down Brings up a Q I keep having: are your miles and my miles the same? Thought it was all kilometers over there. If they are the same...80 mph on a DTR, are you insane?!?! Miranda's expression sez it all.
Moderator Airhead Posted June 4, 2012 Moderator Posted June 4, 2012 .............80 mph on a DTR, are you insane?!?! Miranda's expression sez it all. yep our miles are the same as yours flyday, it was however a DT125R, more powerful than the old MX and all the aerodynamics of a barn door with those big rad scoops up front
Ryan09 Posted June 4, 2012 Posted June 4, 2012 If anything id put a slightly larger rear sprocket on, they arnt made for top speed at the end of the day. That said I dont understand why people find 80mph on a dt hard to beleive?? Mine used to hit 80 if the conditions were right and wringing its neck. (Mine was on stock gearing btw) My old beast: Still kind of miss it.
Moderator DirtyDT Posted June 4, 2012 Moderator Posted June 4, 2012 Brings up a Q I keep having: are your miles and my miles the same? Thought it was all kilometers over there. As Airhead says, miles are the same. Gallons are different.
flyday58 Posted June 4, 2012 Posted June 4, 2012 That said I dont understand why people find 80mph on a dt hard to beleive?? Mine used to hit 80 if the conditions were right and wringing its neck. (Mine was on stock gearing btw) Guess it's the diff between air and water-cooled types. Probably I'm a little gun-shy since the heat seizure, too.
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