I agree that brakes are cheaper to replace, but...

If you were crusing at 60 MPH in 6th gear and needed some passing power, you could downshift into 4th and punch it. What's the difference between that and using the gears to slow down?

Plus, I just dont see why you would rev the motor to shift down, it seems like you'd be popping it into gear. I've just never ever heard of or seen anyone do this.

I mean maybe I wasn't taught to drive stick properly, but it seems like everyone I know used their gears to slow the car down.

 

Downshifting w/o rev matching transfers that shock to your drive train... every bit of it. This is true if you're doing it to speed up or slow down.

As far as downshifting to slow down, other than a couple MPH which you would stay in gear for... or to stop from riding the brakes on a downward slope, I just don't get why you would do this.

As far as why rev the motor to shift down:
When you're at 7K RPM in 2nd gear you're going slower then if you're at 7K in 5th gear, that's a given right. So.. if you're going the same speed in 5th gear that is equivalent to 7K in 2nd gear the RPMs are going to be lower... so when you shift down from 5th to 2nd going the same speed the RPMs of the engine need to rev up to match the speed of the rear wheels (or the rear wheels slow down, which is generally NOT why you're downshifting... and the fact that this transmits a fair bit of shock/stress to your drive train). Hope that makes sense.

-Doug

On edit: oh and let's not forget that downshifting doesn't tell other people behind you that you're slowing down.

 

It's a safety and a control thing. An added plus is engine braking.

It is also not bad practice for autocross and track usage.

See this thread, it has recently been discussed to death here:
Well I only thought I'd do a quick search and find that thread. The search sux I got posts on replacement engines, heel & toe, broken down cars at the track, everything but the thread I wanted.

EDIT: Found it! https://www.s2ki.com/forums/index.ph...ic=401981&st=0
When I did a search for Why should I downshift (the name of the thread) I got nothing. But a search just on downshifting turned it up.

It was very recent and in Under the Hood, Racing or S2000 talk. If you go back several pages in you should find it.

 

Downshifting from 6th to 4th to pass (or if you street race to put you in the proper gear for maximum acceleration) is a perfect example of why you need to learn to downshift properly. The procedure for this downshift is the same as for downshifting to come to a stop except you decelerate rather than accerate.

You have to rev the motor to get the revs to the proper range. If you match the revs when you engage the clutch it is smooth and seamless. You HAVE seen and heard this if you've ever watched Speedvision and seen an inside car shot. ALL racers do it when entering a corner.

 

I found a thread about this on superhonda. They were having the same exact conversation as we are.

Superhonda Forum

I understand the theories being discussed now, but... consider this...

If you had an automatic transmission, and you were slowing down, the transmission is downshifting as you slow down. Surely, you are not straining the engine too much if you are not downshifting at the top of a given gear in the S2000...

Or am I totally wrong about this....?

Tx_Phantom

 

An automatic transmission is a completely different beast... it doesn't know when you're going to press the gas and has to be engaged at all times unless it's shifting... not to mention all of the other technical differences in an automatic.

Given I havn't looked into the automatic transmissions much, I am aware of how they seem to act in other vehicles and with that I say:

Besides it's not downshifting other than when it needs to be in a lower gear... most of the braking power is coming from the brakes, with minimal coming from the engine itself. Besides, there are obvious things an automatic can do that a manual can not... take sitting on a hill for instance. The auto is always engaged, given it's bad to use it to keep you from rolling backwards (instead of using your brakes) but it's still engaged... try that with a manual...

I understand that this method gives you marginally more control over the gas and that variable of control which is great for on the track... but not always on the street. When I'm wanting to slow down: I would rather have more control on the brake (foot engaging brake pedal) than on the gas. There may be situations where you need to speed up more suddenly to avoid an accident but it seems to me there are many more situations where you need to slow down as quickly as possible...

 

Who says it is an either/or thing?

You can have gas and brake control going on at the same time.

No one has ever suggested that you use the engine instead of the brakes, it is used in addition to the brakes.

Read the 5 page thread I posted earlier, it has already gone over most of these points, except the auto transmission thing.

 

Actually Phantom posed the question about going from 4th to 2nd to slow down... he never mentioned that was in addition to using the brakes. Given that because this was a bit vague I may have read into it wrong. He also didn't know what rev-matching was so I have to assume he wasn't doing it, which is what my post was based on.

It seems the basic summary of that other post is:
Downshifting to supplement braking = Good when done right, although it is still debatable as to if there is excessive clutch wear. That includes rev matching and only doing it to a point. It actually seems that it's not so much used as engine braking as it is to keep the engine up to speed and in a reasonable power band ready to use... the engine braking is more of a benefit.

I have wanted to learn to rev match properly and getting into this habit may help me do that on days when the road is empty, but as far as general on the road safety goes I think there is a lot more in the equation that could get much better benefit than doing this. I think our car's capabilities alone give us a huge advantage over other drivers... being alert will give you a huge advantage... being aware of your surroundings gives a huge advantage, ect, and it seems to me that more people need to master those basic techniques before trying to master this one... but I could be wrong.
-Doug

 

Yeah, you could go to extremes doing this but why?

Doug I wasn't taking you to task over the comment on braking, it just seems that on all posts someone decides that this is supposed to be done in lieu of using the brakes when the braking is just a side effect. Although I have had my brakes crumble and I have needed to use this as most of my braking power so as not to ruin a rotor.

I use engine braking/downshifting on a regular basis. I started doing it to make me more proficient on the track. IT WORKED.

But I do not do it in such a manner as to require high revs on the downshift except when I have to brake quickly or am in a great hurry. It is tough to keep it smooth with a high rpm requirement. I try to do it so that I am in the appropriate gear should the light change color or I need to add power to miss a car swerving at the last minute.

All things in moderation.

 

Now that the thread has been hijacked fairly well... did you ever find the problem TJ (Big Bird)?