Question regarding accelerating from stop on snow/ice with manual transmission

[FoMoJo]

The amount of travel in the clutch pedal does not change.  The pressure between the clutch plates for any given point in the pedal travel is the same regardless of gear, and therefore the friction force is the same.  Starting in a higher gear requires you spend more time with the plates slipping, and that you mete out the clutch pedal more slowly in that slipping zone and with greater care to avoid stalling.  The more slipped distance at a given plate pressure, the more wear and tear on the clutch.  2nd gear starts require more delicacy with the clutch, not less.

Once again, if there is more resistance from the pressure plate then more pressure is needed from the clutch disc being pressed against the flywheel which presupposes that the clutch pedal much be released a bit further in order to overcome the resistance; hence a bit more travel needed on the clutch pedal in order to apply more pressure on the clutch disc.

A little more wiggle room on the clutch pedal.

[MX793]

Once again, if there is more resistance from the pressure plate then more pressure is needed from the clutch disc being pressed against the flywheel which presupposes that the clutch pedal much be released a bit further in order to overcome the resistance; hence a bit more travel needed on the clutch pedal in order to apply more pressure on the clutch disc.

A little more wiggle room on the clutch pedal.

That would imply that it's harder to stall, which is incorrect.

More "resistance" at the transmission side means you need more pressure between the plates, but the motor side is constant.  It will still stall if the speed is dragged down by the transmission side.  This means more throttle, more slippage, more heat, and more wear.

[Soup DeVille]

If you can smell clutch; you still have clutch.

[FoMoJo]

That would imply that it's harder to stall, which is incorrect.

More "resistance" at the transmission side means you need more pressure between the plates, but the motor side is constant.  It will still stall if the speed is dragged down by the transmission side.  This means more throttle, more slippage, more heat, and more wear.

That is all correct, which is why it is not a good idea.  However, it still gives you a bit more wiggle room on the clutch pedal.

Try it in high gear and you'll get a lot more slippage before the clutch disc gets a good grip on the flywheel/pressure plate.  If your clutch components are a bit too worn, you'll have the clutch pedal all the way out and it'll still be slipping.

[MX793]

That is all correct, which is why it is not a good idea.  However, it still gives you a bit more wiggle room on the clutch pedal.

Try it in high gear and you'll get a lot more slippage before the clutch disc gets a good grip on the flywheel/pressure plate.  If your clutch components are a bit too worn, you'll have the clutch pedal all the way out and it'll still be slipping.

Not really.  It takes more clutch to get the car moving, but it also pushes you closer to stalling the engine in the process, which means much more slipping.  Starting in 1st is much more forgiving, which is why it's pretty easy in most any vehicle to take off in first without even touching the accelerator.

[FoMoJo]

Not really.  It takes more clutch to get the car moving, but it also pushes you closer to stalling the engine in the process, which means much more slipping.  Starting in 1st is much more forgiving, which is why it's pretty easy in most any vehicle to take off in first without even touching the accelerator.

Yes, much more slipping which is not a good idea. 

I believe its only useful for those who have trouble engaging, or finding the engaging point in the clutch pedal travel.  If you do not have a sensitive and steady foot, you can engage the clutch too suddenly and with more torque applied to the wheels they will slip.  With a higher gear, if you miss the delicate engagement point you will get more slippage within the clutch apparatus and less torque applied to the wheels.  As well, it drags your rpm down quicker and if you don't suddenly tramp on the gas pedal to keep it from stalling, it just might get you moving.

[MX793]

Yes, much more slipping which is not a good idea. 

I believe its only useful for those who have trouble engaging, or finding the engaging point in the clutch pedal travel.  If you do not have a sensitive and steady foot, you can engage the clutch too suddenly and with more torque applied to the wheels they will slip.  With a higher gear, if you miss the delicate engagement point you will get more slippage within the clutch apparatus and less torque applied to the wheels.  As well, it drags your rpm down quicker and if you don't suddenly tramp on the gas pedal to keep it from stalling, it just might get you moving.

The real benefit to starting in 2nd on a slick surface is more what comes after the clutch has fully engaged.  Torque at the wheels at any RPM is reduced, and the rate at which torque increases with vehicle speed is significantly reduced, making it easier to accelerate without spinning the tires.  Likewise, it's usually advisable to keep the car in the highest gear possible, upshifting early, while in the snow since this results in the least torque at the wheels for any speed, both accelerating and under engine braking, meaning you can be less delicate with the accelerator.

[AutobahnSHO]

The faster the engine is going the faster you'll burn the clutch. I find it odd you're slipping wheels that much in a subie??... 

[CaminoRacer]

The point of starting in 2nd is that he could get it a bit of throttle and engage the clutch quickly without accelerating as quickly as he would in 1st.

[FoMoJo]

The real benefit to starting in 2nd on a slick surface is more what comes after the clutch has fully engaged.  Torque at the wheels at any RPM is reduced, and the rate at which torque increases with vehicle speed is significantly reduced, making it easier to accelerate without spinning the tires.  Likewise, it's usually advisable to keep the car in the highest gear possible, upshifting early, while in the snow since this results in the least torque at the wheels for any speed, both accelerating and under engine braking, meaning you can be less delicate with the accelerator.

That's true as well, but the point was getting it going on a slippery surface without spinning the wheels.

[Soup DeVille]

I just gotta think, you guys are way overcomplicating this.

[FoMoJo]

The point of starting in 2nd is that he could get it a bit of throttle and engage the clutch quickly without accelerating as quickly as he would in 1st.

If you're sitting on an icy surface on a uphill grade and engage the clutch quickly, all you would accomplish is having the wheels spin faster.

[MX793]

That's true as well, but the point was getting it going on a slippery surface without spinning the wheels.

Simply letting out the clutch in 1st on a slick surface without touching the throttle will get the car moving with very little wheelspin.  But you need to be very ginger with the throttle once the clutch is out.

[FoMoJo]

Simply letting out the clutch in 1st on a slick surface without touching the throttle will get the car moving with very little wheelspin.  But you need to be very ginger with the throttle once the clutch is out.

Didn't he say he stalled when he did that?  I've lost track.

[MX793]

Didn't he say he stalled when he did that?  I've lost track.

Yes, but that could be a technique issue (letting the clutch out too quickly once the friction point is reached).  Bear in mind the original post complained of burnt clutch and excessive wheelspin on a snowy driveway in an AWD vehicle taking off in 1st.

[Laconian]

Don't AT cars roast their diff clutch packs when driving in snow?

[MX793]

Don't AT cars roast their diff clutch packs when driving in snow?

If you have a friction based differential, excessive wheelspin can wear the clutch pack out.  You can blow an open differential with excess wheelspin.

[FoMoJo]

Yes, but that could be a technique issue (letting the clutch out too quickly once the friction point is reached).  Bear in mind the original post complained of burnt clutch and excessive wheelspin on a snowy driveway in an AWD vehicle taking off in 1st.

Yes, I believe that's what we're discussing, a technique issue.

My advice is is to practice until he can delicately engage the clutch, even briefly holding it at the engagement point until he gets a good feel for it and even more delicately engaging the throttle to prevent it from stalling as once again, delicately engaging the clutch to slowly apply the torque to the wheels.  Once some movement is accomplished a little more throttle can be applied.

[Soup DeVille]

Don't AT cars roast their diff clutch packs when driving in snow?

They can, if you drive like you're not on snow, or drive like you're Petter Solberg on snow.

[veeman]

I tried again this morning on my driveway.  Most of the snow/ice is melted but there was still a good 15 ft x 15 ft patch of 1/2 in thick ice a few feet from my garage door so it was perfect.  I centered the Subie Craptrek on it.  Because of the angle of the driveway with respect to the garage door, my front wheels were turned 45 degrees.  Incline is about 5 degrees. 

1. I park the car.  Foot on brake and clutch depressed I release the hand brake and put it in 1st gear.  Slowly release clutch with foot completely off of brake.  Car doesn't move forward.  Just stands there.  I'm pretty confident this is not an error of mine. I will stall unless I give throttle or I depress the clutch again. 

2. I do exactly what MX793 told me to do.  I depress clutch all the way and very gingerly give throttle. (by the way the car idles at 1800 rpm when in neutral with foot off of the throttle and handbrake engaged)... anyways I very gingerly give throttle and keep RPM as much as I can around 1500.  I'm f_cking concentrating man.  I slowly release clutch, if I feel like the car is going to stall, I only modulate the clutch and I keep the throttle as much as possible around 1500 rpm and not higher.
Voila!... the car smoothly goes into the open garage with no wheel spin.  I get out and don't smell any burning.  F_ck yeah!!  Sweet!  I repeat the maneuver two more times.  Each time smooth forward movement and no burning. Thanks man!!

I don't think the ice will stick around for another night so I'll have to practice probably again next year.  But honestly I feel pretty good. 

Question: the one thing I'm thinking is this method is great for snow/ice covered driveways but isn't that great when at a stop light or stop sign on snow covered roads because I like to accelerate fast and controlled wheel spin is kinda cool.  But I don't want to burn the clutch.  In this situation in the future, should I just do what CaminoRacer suggested and start in 2nd gear, give wide open throttle, and pop the clutch.  I think what I have been doing is giving wide open throttle in 1st gear while popping the clutch.  Car jerks, tires spin, I go forward fast, but no burn smell.  Is popping the clutch significantly bad for the clutch or bad for the car in general?  On my driveway I don't want to give a lot of throttle and pop the clutch because I don't want to go fast and spin the wheels.  Especially near my garage. 

[MX793]

1800 RPM is a really high idle unless the engine is cold.  Every car I've ever owned idled under 1000 when at operating temperature.

Does the Crosstrek have hill-hold assist?  That might be part of the issue.

[veeman]

1800 RPM is a really high idle unless the engine is cold.  Every car I've ever owned idled under 1000 when at operating temperature.

Does the Crosstrek have hill-hold assist?  That might be part of the issue.

Car wasn't that cold (I drove it about 3 hours ago and my garage is somewhat insulated).  Craptrek does have hill assist.  But I just googled and it can be disabled.  Should I disable it?  My prior VW Beetle (I just googled) also had hill assist so I guess my experience in driving manual transmission cars regularly has been with hill assist on.  So I don't know if I would go backwards when starting on a significant incline without it.  I don't think I would because I had driven occasionally manual transmission cars in my youth without hill assist.  But that was many years ago and I didn't drive them a lot.   

[veeman]

If disabling hill assist will increase the life span of my clutch, I will definitely disable it. 

[MX793]

3 hours is long enough for oil and coolant to cool down to room temperature, and I assume your garage is not heated.  Normal idle should be around 800 RPM.

I have limited experience with hill hold.  My current Mustang has it and I didn't care for it and disabled it within the first week of ownership.  I didn't stall because of it, but I could see how it might make starts a little harder.  However, I learned to drive stick without it and had over 15 years of driving stick to refine my technique.  If you've never driven without it, you'll need to make some adjustment to your driving style and re-learn how to start on hills.

[CaminoRacer]

Question: the one thing I'm thinking is this method is great for snow/ice covered driveways but isn't that great when at a stop light or stop sign on snow covered roads because I like to accelerate fast and controlled wheel spin is kinda cool.  But I don't want to burn the clutch.  In this situation in the future, should I just do what CaminoRacer suggested and start in 2nd gear, give wide open throttle, and pop the clutch.  I think what I have been doing is giving wide open throttle in 1st gear while popping the clutch.  Car jerks, tires spin, I go forward fast, but no burn smell.  Is popping the clutch significantly bad for the clutch or bad for the car in general?  On my driveway I don't want to give a lot of throttle and pop the clutch because I don't want to go fast and spin the wheels.  Especially near my garage. 

It's not bad for the clutch but it can be very hard on the drivetrain (differential, CV joints, etc) since instead of the clutch taking the brunt of the torque, it goes straight to the drivetrain and wheels. If it's snowy and the road is slick, you'd be unlikely to harm anything since the tires will spin. Spinning tires are good to avoid breaking things in the drivetrain, since the energy is able to "escape" into motion. But like MX has said, spinning the tires too fast can wear out the differential too. So 2nd gear should only be used when 1st gear spins the tires too much in the snow. It's a balancing act between spinning the tires and being nice to the clutch.

Letting the clutch out slowly at idle is unlikely to wear out the clutch. But revving the engine at higher rpms (2,000+) and letting the clutch out slowly will wear it out pretty quick and that's when you'll start smelling it. So the best options are 1. be gentle on the throttle and let the clutch out slowly or 2. be aggressive on the throttle and dump the clutch so it doesn't have time to wear out. I only do #2 when racing/autocrossing, because it's incredibly obnoxious on the street and does have the potential to break axles/differentials like mentioned before.

[Laconian]

1800 RPM is a really high idle unless the engine is cold.  Every car I've ever owned idled under 1000 when at operating temperature.

Does the Crosstrek have hill-hold assist?  That might be part of the issue.

My Subie 2.5 has a high initial idle which drops down after 30 seconds or so.

[MX793]

My Subie 2.5 has a high initial idle which drops down after 30 seconds or so.

Yeah, most cars will have a high idle on initial startup.

[CaminoRacer]

I usually wait for my idle to drop to around 1100 before I start moving. Only takes a few seconds but it lets the engine start running on a more normal fuel mixture (instead of being very rich) and also gives the oil a little bit of time to get up to the top of the heads.

[veeman]

While leaving work this morning I checked the Craptrek's RPM at idle when first starting the car (it had been parked in the garage at work overnight).  It was 1800 RPM.  Five minutes later, at a stop light, I checked the idle again.  It was now at 800 RPM.  You guys are correct. 

I have heard that for the last few decades, there is no need to warm up a car prior to driving off.  You don't need to do that with modern cars.  I can't really do that anyways at my work because people are always searching for parking spots and they expect you to leave the spot as soon as you get in your car.  Whatever.  I'm not a sit in my car without driving off type of person.   

[MX793]

You should let a car idle for about 30 seconds before driving.  And then avoid hard driving until it is up to temperature (which should only take 5 minutes of driving).  Idling until up to full temp is also not good for the car.