Why Do Only Burned Audio Cd's Jump When Played from Your Car Cd Player?

I have been burning my dad's favorite songs from the 60's and 70's to audio CD's for about 4 months now so he can play them in his car. He complains that near the end of the CD's the songs start to jerk and jump and skip, especially when he goes over bumpy ground. There is one exception though. CD 3 seems to be immune to jumping and I burned it exactly the same way as most of the other CD's. This confuses the hell out of me and seems to be random.

Here are some facts about the CD's that might help:

A) The CD's are all of the same quality. They are low quality CD's I bought from CNA. Not sure exactly what make they are. It doesn't specify.
B) I have been burning the CD's all from the same CD-rom drive on the same computer.
C) There are about 26 songs on each CD. I try to get as close to 80 minutes as possible to make the most of space.
D) Before I burn any audio CD I always select the option that sets all the songs to play at the same volume since the songs have come from many different albums and other formats.
E) I downloaded most the songs in mp3 format that I placed on the CD's.
F) I have burned most of the CD's at 40x speed.

Here are a few possible solutions I dug up by googling the problem:

1) Burn CD at 24x speed. Apparently car CD's read at only one speed and they have a weaker lazer than other standard CD players to prolong the life of the car battery. I have experimented with some of the CD's, burning them at every other speed except for 24x. I'm yet to try that.
2) Use higher quality CD's. I honestly don't see how that could work. Never heard of it.
3) Get a car CD player that has a read ahead buffer. That's expensive and what if it doesn't work?
4) Make sure the songs are under 60 minutes on each CD. I tried that and it makes no difference.

I'd appreciate it if you guys know something I don't.

Suggestion:

CD's should have more than 79 minutes and 59 seconds on them.

And burn it at 24x or get an ipod with portable speakers for your dad…