Ramp angles and static lock are two different things. Static lock dictates how much locking power the LSD unit has, such that with a 25% lock LSD, the clutchs allow 75% slippage, so essentially if the inside wheel is moving at 100mph, the outside wheel may only be turning 25. Not a very accurate explaination, but it gets the idea across. Thus, with a stock LSD, often you will still be able to have it kind of open up on occasions, depending on conditions. This is greatly affected if you have different types or brands of tires, bad alignment, etc... While the wheels stay locked together as they should, the inside wheel will be turning at a much higher rate of speed. So 25% of the power is going to the outside tire, and and 75% is going to the inside tire.
Ramp angles are the way the clutch packs engage though the gearing. The OEM diff is very conservative, to save clutches and to promote the life of the differential. On motorsport diffs and ones that see frequent rebuilds, they are much more agressive. So in any case, when you accellerate out of a turn, one wheel will always have more grip then another, physics of roll and rubber, etc.. A factory LSD with conservative ramp angles will take perhaps a second before locking. On a 150rwhp car, this is not really an issue. You will doubtfully have enough power to spin a wheel exiting a turn at 80mph. This is also why under almost any circumstances, an open differential is fine for a stock car. On a higher HP car, or one with a ton of grip looking for the edge in accelleration, this second can mean a loss of time or an undue wear on tires. So they alter the way the clutch packs engage so that rather then it taking a second to engage, it takes maybe a millisecond. Combined with a higher static lock, this translates into much more grip leaving a turn, and in turn, means higher exit speeds.
In drifting you experience something completely different. The goal is not to have more grip on exit, but more control when there is little grip. You may not care about the characteristics of your car at a track day, but when it comes time to doing a clutch kick at a D1 event, you want to know that your rear is going to be locked and stay locked. This is more of a static lock issue then a ramp angle issue as your applying enough power to lock the differential with ease. Why altering the ramp angles may be beneficial is when you choose to power-over instead of clutch kicking (aka, power sliding), you need 100% control. Many drifters in AE86's and 240's just weld the diffs so there is 100% lock at all times. This will snap if the wheel aren't spinning (such as at a track), but will provide the most control in a drifting environment.
I don't rebuild differentials very often, nor do I have the tools capable of doing many of things I suggest. I have rebuilt diffs before, but like most, just with replacement parts. When it comes to altering ramp angles, creating more static lock, etc..., its best to consult a professional. Its not a hard part to break if you do something wrong, but it can be annoying and tiresome to have to keep doing it over to get it right. There is a specific tool for altering ramp angles, and of course its expensive, so you pay for what you get. I have had an account with KAAZ because they make that job much easier by providing everything I want all ready to go (when I was in the Porsche arena).
Wes
Ramp angles are the way the clutch packs engage though the gearing. The OEM diff is very conservative, to save clutches and to promote the life of the differential. On motorsport diffs and ones that see frequent rebuilds, they are much more agressive. So in any case, when you accellerate out of a turn, one wheel will always have more grip then another, physics of roll and rubber, etc.. A factory LSD with conservative ramp angles will take perhaps a second before locking. On a 150rwhp car, this is not really an issue. You will doubtfully have enough power to spin a wheel exiting a turn at 80mph. This is also why under almost any circumstances, an open differential is fine for a stock car. On a higher HP car, or one with a ton of grip looking for the edge in accelleration, this second can mean a loss of time or an undue wear on tires. So they alter the way the clutch packs engage so that rather then it taking a second to engage, it takes maybe a millisecond. Combined with a higher static lock, this translates into much more grip leaving a turn, and in turn, means higher exit speeds.
In drifting you experience something completely different. The goal is not to have more grip on exit, but more control when there is little grip. You may not care about the characteristics of your car at a track day, but when it comes time to doing a clutch kick at a D1 event, you want to know that your rear is going to be locked and stay locked. This is more of a static lock issue then a ramp angle issue as your applying enough power to lock the differential with ease. Why altering the ramp angles may be beneficial is when you choose to power-over instead of clutch kicking (aka, power sliding), you need 100% control. Many drifters in AE86's and 240's just weld the diffs so there is 100% lock at all times. This will snap if the wheel aren't spinning (such as at a track), but will provide the most control in a drifting environment.
I don't rebuild differentials very often, nor do I have the tools capable of doing many of things I suggest. I have rebuilt diffs before, but like most, just with replacement parts. When it comes to altering ramp angles, creating more static lock, etc..., its best to consult a professional. Its not a hard part to break if you do something wrong, but it can be annoying and tiresome to have to keep doing it over to get it right. There is a specific tool for altering ramp angles, and of course its expensive, so you pay for what you get. I have had an account with KAAZ because they make that job much easier by providing everything I want all ready to go (when I was in the Porsche arena).
Wes
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